Disease and Its Causes Part 7

Imperfections of the heart which interfere with its action may be the result of failure of development or disease. An imperfect heart which can, however, fully meet the limited demands made upon it in intra-uterine life, may be incapable of the work placed upon it in extra-uterine life. Children with imperfectly formed hearts may be otherwise perfect at birth, but they have a bluish color due to the imperfect supply of the blood with oxygen, and are known as blue babies. The condition becomes progressively worse due to the progressive demands made upon the heart, and death takes place after some days or months or years, the time depending upon the degree of the imperfection.

Much of the damage of the heart in later life is due to infection. The valves of the heart are a favorite place for attack by certain sorts of bacteria which get into the blood. This is due to the prominent position of the valves which brings them in contact with all the blood in the body, the large extent and unevenness of the surface and to the rubbing together and contact of their edges when closed. At the site of infection there is a slight destruction of tissue and on this the blood clots producing rough wart-like projections. The valves in some cases are to a greater or less extent destroyed, they may become greatly thickened and by the deposit of lime salts converted into hard, stony ma.s.ses. Essentially two conditions are produced. In one the thickened, unyielding valves project across the openings they should guard, and thus by constricting the opening interfere with the pa.s.sage of blood either through the heart or from it. In the other the valves are so damaged that they cannot properly close the orifices they guard, and on or after the contraction of the cavities there is back flow or regurgitation of the blood. If, for instance, the orifice of the heart into the aorta is narrowed, then the left ventricle can only accomplish its work of projecting into the aorta a given amount of blood in a given time by contracting with greater force and giving a greater rapidity to the stream pa.s.sing through the narrow orifice.

This the heart can do because, like all other organs of the body, it has a large reserve force which enables it, even suddenly, to meet demands double the usual, and like all other muscles of the body it becomes larger and stronger by increased work. The condition here is much simpler than when the same valve is incapable of perfect closure, or when both obstruction and imperfect closure, are combined as they not infrequently are. In such cases the ventricle must do more than in the first case. It must force through the orifice, which may be narrowed, the amount of blood which is necessary to keep up the pressure within the aorta and give to the circulation the necessary rapidity of flow, and also the amount which flows back into the heart through the imperfectly acting valve. This it can do by contracting with greater force upon a larger amount of blood, the cavity becoming enlarged to receive this. Not only may such damage to the valves be produced, but the muscular tissue of the heart may suffer from defective nutrition or from the effect of poisons, whether these are formed in the body as the effect of disease or introduced from without; or in consequence of disease in the lungs the flow of blood through them may be impeded, or disease elsewhere in the body, as in the kidneys may, by increasing the pressure of the blood within the arteries, throw more than the usual amount of work upon the heart.

The power of the heart in meeting these conditions, however various they are and however variously they act, seems little short of marvellous, and it goes on throwing three and one-third ounces of blood seventy or eighty times a minute into a tube against nine feet of water pressure, working often perfectly under conditions which would be fatal to a machine. As long as this goes on the injury is said to be compensated for; the increased work which the heart is able to accomplish by the exercise of its reserve force and by becoming larger and stronger enables it to cope with the adverse conditions.

With increased demand for work there is a gradual diminution of the reserve force. An individual may be able to carry easily forty pounds up a hill and by exerting all his force may carry eighty pounds, but if he habitually carries the eighty pounds, even though the muscles become stronger by exercise the load cannot be again doubled. The dilatation of the heart which is so important in compensation is fraught with danger, because any weakening of the muscle increases the dilatation, until a point is reached when, owing to the dilatation of the orifices between auricles and ventricles, the valves become incompetent to close them.

When the heart is not able to accomplish its work, the effect of the condition becomes apparent by the acc.u.mulation of blood within the veins and a less active circulation. This affects the nutrition and the capacity for work of all the organs of the body, and the imperfect function of the organs may in a variety of ways make still greater demands upon an already overloaded heart. Other conditions supervene.

The increased pressure within the veins and capillaries due to the impossibility of the blood in the usual amount pa.s.sing through or from the heart increases the amount of fluid in the tissues. There is always an interchange between the blood within the vessels and the fluid outside of them; the pa.s.sage of fluid from the vessels is facilitated by the increased pressure within them, just as pressure upon a filtering fluid increases the rapidity of filtration, and the increase of pressure within veins and capillaries impedes pa.s.sage of tissue fluid into them. The fluid acc.u.mulates within the tissues leading to dropsy, or the acc.u.mulation may take place in some of the cavities of the body. The diminished flow of blood through the lungs prevents its proper oxygenation; this may also be interfered with by the acc.u.mulation of fluid within the air s.p.a.ces of the lungs.

Every additional burden thrown upon the heart increases the evil. In women the additional burden of pregnancy may suffice to overcome a compensation which has been perfect, and the same may result from an acute attack of disease. Age, diminis.h.i.+ng as it does the capacity for work in all organs, diminishes the compensation capacity of the heart, and a heart which at the age of forty acts perfectly may break down at the age of fifty. Compensation may be gained in other ways, as by reducing the demand made upon the heart by changing the mode of life, by leading an inactive rather than an active life, by avoiding excitement or any condition which entails work of the heart. Social conditions are of great importance; it makes a great difference whether the unfortunate possessor of such a heart be a stevedore whose capital lies in the strength of his muscles, or a more fortunately placed member of society for whom the stevedore works and whose occupation or lack of occupation does not interfere with the adjustment of his external relations to the condition of his heart.

Disease of the nervous system does not differ from disease elsewhere.

The system is complex in structure and in function. It consists in nerves which are composed of very fine fibrils distributed in all parts of the body and serve the purpose of conduction, and a central body composed of the brain and spinal cord which is largely cellular in character; it receives impressions by means of the nerves and sends out impulses which produce or affect action in all parts. By means of the organs of special sense, the brain receives impressions from the outer world which it transforms into the concepts of consciousness.

Many of the impressions which the central nervous system receives from nerves other than those of special sense and even many of the impressions from these and the impulses which it sends out do not affect consciousness. The memory faculty is seated in the brain and all parts of the brain are closely connected by means of small nerve fibres. The nervous system plays an important part in the internal regulation and coordination of all parts of the body, and it is by means of this that the general adjustment of man with his environment is effected.

Malformations of the brain, except very gross conditions which are incompatible with extra-uterine existence, are not very common. At birth those parts of the brain which are the seat of memory and what are understood as the higher faculties are very imperfectly developed.

Variations in structure are extremely common, there are differences in different individuals in the nerves and in the number, size, form and arrangement of the nerve cells, and so complex is the structure that considerable variation can exist without detection. The tissue of the central nervous system has a considerable degree of resistance to the action of bacteria, but is, however, very susceptible to injury by means of poisons. Serious injury or destruction of tissue of the brain and spinal cord is never regenerated or repaired, but adjustment to such conditions may be effected by reciprocity of function, other cells taking up the functions of those which were destroyed.

Certain parts of the brain are a.s.sociated with definite functions; thus, there are areas which influence or control speech and motion of parts as the arm or leg, and there are large areas known as the silent areas whose function we do not know. All activity of the central nervous system, however expressed, is due to cell activity and is a.s.sociated with consumption of cell material which is renewed in periods of repose and sleep. Fig. 13 shows a nerve cell of a sparrow at the end of a day's activity and the same after the repose of a night.

Diseases of the nervous system have a special interest in that they so often interfere with man in his relations with his fellows. In diseases of other organs the disturbances set up concern the individual only. Thus, others need not be disturbed save by the demands made on their sympathies by an individual with a cold in the head or a cancer of the stomach. Disease of the nervous system is another affair, instead of those reactions and expressions of activity to which we are accustomed and to which society is adjusted, the reactions and activities are unusual and the individual in consequence does not fit into the social state and is said to be anti-social.

There are all possible grades of this, from mere unpleasantness in the social relations with such an individual, to states in which he is dangerous to society and must be isolated from it. Insanity is an extreme case. There is no disease signified in the expression, but it is merely a legal term to designate those individuals whose actions are opposed to the social state and who are not responsible for them.

In insanity there is falsity in impressions, in conceptions, in judgment, a defective power of will and an uncontrollable violence of emotion. The individual is prevented from thinking the thoughts or feeling the feelings and doing the duties of the social body in the community in which he lives. The insane are out of harmony with their social environment, but not necessarily in opposition to it.

There is no very sharp line between insanity and criminality. The criminal is in direct antagonism to the laws of social life. An insane person may cause the same injury to society as a criminal, but his actions are not voluntary, whereas the criminal is one who can control his actions, but does not. Mentally degenerated persons, however, can be both insane and criminal. Whatever the state of society, this reprobates the actions of one opposed to it; in a society in which it were usual to appropriate the possessions of others or to devour unpleasant or useless relatives, virtue and lack of appet.i.te would be reprobated as unsocial.

The symptoms of insanity or the manner in which the defective action of the brain expresses itself and the various underlying pathological changes vary, and by combining these it has been possible to subdivide insanity into a number of distinct forms. There are both intrinsic and extrinsic causes of insanity. The intrinsic are the structural differences in the brain as compared with the normal or usual, whether these are due to imperfection in development or to defective heredity or to the injury of disease; the extrinsic causes are those which come from without and bring the intrinsic into activity. Syphilis is a frequent cause of insanity, and probably the only cause of the condition known as general paralysis of the insane, acting by means of the injury which it produces in the cortex of the brain. The abuse of alcohol is another fertile cause, but the changes produced in this are not so obvious as in the case of syphilis. Tumors of the brain are not infrequently a cause, and the same is true of infections, even those not located in the brain. How susceptible the brain is to the effects of the toxines of the infectious diseases is shown in the frequency of delirium in these diseases. There is an interesting relation between this and alcoholism. Alcohol abuse may produce injury, but not sufficient to manifest itself under ordinary conditions; when, however, the action of toxic substance is superadded to the effect of the alcohol the delirium of fever is more marked.

Probably of greater importance than the acquired pathological conditions of the brain in producing insanity is a congenital condition in which the nervous system is defective. The most fertile cause of insanity lies in the inheritance; by this it must not be understood that insane parents produce insane offsprings, but that conditions inherited from immediate or remote ancestors appear in a diminished resistance of the nervous system which is sooner or later expressed as insanity. Given such a defective nervous system, extrinsic conditions which would have no effect on another individual or would be felt in different ways may produce insanity. In these cases occupation plays a great role. The excitement and privations of war especially in the tropics and the ennui of camps leads to insanity in soldiers; occupations such as that of the baker in which there is loss of sleep and the mental strain of students can all act in the same way. A woman who gives no sign of nervous defect may become insane under the strain of pregnancy.

Although insanity is determined by the social relations of man, that part of the social organization which is termed _Society_, and which has been developed by the idle as a diverting game, is a fertile source of nervous disease and even of insanity, affecting particularly females. The strenuosity of the life, the nervous excitement alternating with ennui, the lack and improper times of sleep, the lack of rest and particularly of restful occupation, the not infrequent use of alcohol in injurious amounts, are all factors calculated to make a defect operative. The so-called "coming out" of young girls is an important element in the game, and their headlong plunge into such a life at a period under any conditions full of danger to the nervous system is especially to be reprobated. If we consider the influence of the game in other respects as conducing to lack of moral sense, to alcoholic abuse (for without the seeming stimulation, but which is really the blunting of impressions which alcohol brings, the game would not be possible), to discontent, to mental enfeeblement, it is all bad. Curiously enough the game is one which in all periods has been played by the idle, but its evil influence is greater now than before when it was the game of royalty chiefly, because there are now more people living from the work of others.

The unusual mental action of the insane not infrequently expresses itself by suicide. The a.n.a.lysis of three hundred deaths from suicide showed pathological changes in the brain in forty-three per cent, and when we think that mental disturbances are very often without recognizable anatomical changes after death, the percentage is very large. In another a.n.a.lysis of one hundred and twenty-four suicides forty-four of these were mentally affected to various degrees. Five of the men and seven women were epileptics, in ten of the families there was hysteria, twenty-four of the men and four of the women were chronic alcoholics.

It is extremely difficult at the present time to say whether insanity is increasing. Statistics in all lands giving the numbers committed to insane hospitals show on their face a great increase, but so many factors enter into these statistics that their value is uncertain.

There is now an ever-increasing provision for the care of the insane.

Owing to the recognition of insanity as a part of nervous disease and its separation from criminality there is no longer the same attempt to conceal it as was formerly the case, and hospitals for the insane are no longer a.s.sociated with ideas of Bedlam. It is generally believed that modern conditions in the hurry and excitement of life, and the extreme social differences, the greater urban life, the greater extension of factory life, all tend to an increase in insanity, but there is no absolute proof that this is true. We know very little about insanity in the Middle Ages, but the conditions then were not conducive to a quiet life. There prevailed then as now excess and want, luxury and poverty, enjoyment and deprivations, b.a.l.l.s and dinner parties and other features of the social game. There were factions in the cities, public executions, not infrequent sieges, scenes of horror, epidemics, famines, and all these combined with religious superst.i.tion and the often unjust and cruel laws should have been factors for insanity. There were actual epidemics of insanity affecting ma.s.ses of the population, as shown in the children's crusade, the Jewish ma.s.sacres and the dancing mania in the Rhine provinces. Where civilization seems to be the highest, statistics show the most insane, but this most probably depends upon better recognition of the condition and better provision for asylum care.

The so-called functional diseases have a close relation with diseases of the nervous system, for they chiefly concern the reactions of nerve tissue. Disease expressing itself in disturbance of function only, does not seem to fit in with the conceptions of disease which have been expressed, nor can we imagine a disturbance of function which does not depend upon a change of material. Living matter does not differ intrinsically from any other sort of matter; like other matter its reactions depend upon its composition structure[1] and the character of the action exerted upon it. By functional disease there is expressed merely that no anatomical or chemical change is discoverable in the material which gives the unusual reaction. The further our researches into the nature of disease extend, particularly the researches into the physiology and chemistry of disease, the smaller is the area of functional disease. In functional disease there may be either vague discomfort or actual pain under conditions when usually such would not be experienced, and on examination no condition is found which in the vast majority of cases would alone give rise to that impression on the nervous system which is interpreted as pain. In the production of the sensations of disease there can be change at any place along the line, in the sense organs, in the conducting paths or in the central organ. Thus there may be false visual impressions which may be due to changes in the retina or in the optic nerve or in the brain matter to which the nerve is distributed. It is perfectly possible that substances of an unusual character or an excess or deficiency of usual substances in the fluids around brain cells may so change them that such unusual reactions appear. There may be, of course, very marked individual susceptibility, which may be congenital or acquired. The perception of every stimulus involves activity of the nerve cells, and it is possible that the constant repet.i.tion of stimuli of an ordinary character may produce sufficient change to give rise to unusual reactions, and this particularly when there is lack of the restoration which repose and sleep bring. We know into what a condition one's nervous system may be thrown by the incessant noise attending the erection of a building in the vicinity of one's house or the pounding of a plumber working within the house, this being accentuated in the latter case by the thought of impending financial disaster. Even the confused and disagreeable sound due to the clatter of high-pitched women's voices at teas and receptions may, when frequently repeated, be productive of changes in the nerve cells sufficiently marked to give rise to the unusual reactions which are evidence of disease.

In the condition known as neurasthenia, which is often taken as a type of a functional disease, the basal and intrinsic cause is activity of the nervous system with the using up of material which is not compensated for by the renewal which comes in repose and sleep.

Neurasthenia is one of the common conditions of our civilization, found among children and adults, the poor and rich, the idle and the factory worker; it is rife in the scholastic professions and among those who earn their living by brain work. It seems to be more common in the upper cla.s.ses and particularly in the women, but this is because these are more subject to medical care and the condition is more in evidence. There are all sorts of symptoms attached to the condition, for the unusual mental action can be variously expressed.

The cerebral form has been thus described by a well-known medical writer: "One of the most characteristic features of cerebral neurasthenia is a weary brain. The sensation is familiar enough to any f.a.gged man, especially if he fall short of sleep. Impressions seem to go half into one's head and there sink into a woolly bed and die.

Voices sound far off, the lines of a book run into one another and the meaning of them pa.s.ses unperceived. Doors bang and windows rattle as they never did before; if a shoestring breaks, an imprecation is upon the lips. Business matters are in a conspiracy to go wrong. Letters are left unopened partly from want of will, partly from a senseless dread lest they contain bad news. At night the patient tosses on his bed possessed by all the cares which blacken with darkness. Headache is common, loss of memory is distressing, and in severe cases it is wider and deeper than mere inattention can explain. There is often the torture of acute hearing, or an inability to suppress attention; the hater of clocks and crowing c.o.c.ks is a neurasthenic." The disease is especially common in the women players of the social game, and its unhappy victims too often seek relief from the nervous irritability which is a common early symptom in still greater nervous excitement.

It is a sad commentary on our civilization that one of the means of treatment for these persons which has been found efficacious is to supply them with some restful household occupation such as knitting or plain sewing, and there are inst.i.tutions which combine refuge from social activities, often called duties, with simple occupation.

FOOTNOTE: [1] By structure as used in this wide sense, there must be understood not merely the anatomical structure, which is revealed by the dissecting knife and microscope, but molecular structure, or the manner in which elements are arranged to form the molecule, as well.

CHAPTER XII

THE RAPID DEVELOPMENT OF MEDICINE IN THE LAST FIFTY YEARS.--THE INFLUENCE OF DARWIN.--PREVENTIVE MEDICINE.--THE DISSEMINATION OF MEDICAL KNOWLEDGE.--THE DEVELOPMENT OF CONDITIONS IN RECENT YEARS WHICH ACT AS FACTORS OF DISEASE.--FACTORY LIFE.--URBAN LIFE.--THE INCREASE OF COMMUNICATION BETWEEN PEOPLES.--THE INTRODUCTION OF PLANT PARASITES.--THE INCREASE IN ASYLUM LIFE.--INFANT MORTALITY.--WEALTH AND POVERTY AS FACTORS IN DISEASE.

Certain conditions have arisen in the past fifty years which have profoundly affected the thoughts, the beliefs and the activities of man. Within this period what is generally known as Darwinism, including under this evolution, has developed. Unlike theories which came from philosophical speculation only, the theory of evolution was one which could be subjected to observation and experiment. It freed man's mind from dogmas, it stimulated the imagination, it enlarged the territory in which it seemed possible to extend knowledge by the methods of science, and has resulted in an enormous increase of knowledge. This has been more striking in medical science than elsewhere, and in this of more far-reaching influence. Evolution coincided with another important development. History shows that all great periods of civilization have at their back sources of energy. In the civilizations of the past such sources of energy have come from the enslavement of conquered peoples or from commerce, or more direct forms of robbery, which have enabled a favored cla.s.s to appropriate for its purposes the results of the work of others. While these sources have not been absent in the development of our civilization, the great source of energy has come from the rapid, and usually wasteful and reckless, utilization of the stored energy of the earth.

The almost incredible advance in medical and other forms of scientific knowledge and the utilization of this knowledge is largely due to the greater forces which we have become possessed of.

Disease plays such a large part in the life of man and is so closely related to all of his activities that the changes in this period must have exerted an influence on disease. We have already seen that within the period we have obtained knowledge of the causes of disease and the conditions under which these causes became operative. The mystery which formerly enveloped disease is gone; disease is recognized as due to conditions which for the most part are within the control of man, and like gravity and chemical attraction it follows the operation of definite laws. There has been developed within the period what is known as preventive medicine, which aims rather at prevention than cure, and the resources of prevention are capable of much greater extension.

Have there been new conditions developed within the period, or an increase of existing conditions which can be regarded as disease factors and which counterbalance the results which have come from the knowledge of prevention and cure? There has been an increase of certain factors of immense importance in the extension of disease.

These are:

1. The increase in industrialism, involving as this does an increase in factory life. In many ways this is a factor in disease. (_a_) By favoring the extension of infection, particularly in such diseases as tuberculosis. (_b_) The life indoors, and frequently with the combination of insufficient air and s.p.a.ce, produces a condition of malnutrition and deficient general resistance. (_c_) The family life is interfered with by the mothers, whose primary duty is the care of home and children, working in factories, and the too frequent conversion of the house into a factory. (_d_) The influence of factory life is towards a loss of moral stamina rendering more easy of operation the conditions of alcoholism and general immorality. How great has been this increase in industrialism, fostered as it has been by conditions both natural and artificially created by unwise legislation, is shown in the figures from the last census. The number of factory operatives increased forty per cent between 1899 and 1909 and the total population of the country in the period between 1900 and 1910 increased twenty per cent. It is probable that the future will see an extension rather than a diminution of ma.s.s labor.

2. The increase in urban life is as conspicuous as the increase in industrialism. In 1880, twenty-nine and five-tenths per cent of the population was urban and seventy and five-tenths per cent was rural; in 1910, forty-six and three-tenths per cent was urban and fifty-three and seven-tenths was rural, the increase being most marked in cities of over five hundred thousand inhabitants. Of the total increase in population between 1900 and 1910, seven-tenths per cent was in the cities and three-tenths per cent in the country. City life in itself is not necessarily unhealthy and there are many advantages a.s.sociated with it. The conditions which have chiefly fostered it are the immigration of people who are accustomed to community life, the increase in factory life and the increased number of people of wealth who seek the advantages which the city gives them. The city has always been the favored playground for the social game. The unhealthy conditions of city life are due to the crowding, the more uncertain means of livelihood, the greater influence of vice and alcoholism.

Prost.i.tution and the s.e.xual diseases are almost the prerogatives of the cities.

3. All means of transportation have increased and communication between peoples has become more extended and more rapid. In the past isolation was one of the safeguards of the people against disease.

With the increase and greater rapidity of communication there is a tendency not only to loss of individuality in nations as expressed in dress, customs, traditions and beliefs, but many diseases are no longer so strictly local as formerly--pellagra, for example. Only those diseases which are transmitted by insects which have a strictly local habitat remain endemic, although the region of endemic prevalence may become greatly extended, as is seen in the distribution of sleeping sickness. Diseases of plants and of animals have become disseminated. Any plants desirable for economic use or for beauty of foliage and flower become generally distributed, their parasites are removed from the regions where harmonious parasitic inter-relations have been established, and in new regions the parasites may not find the former restrictions to their growth. There have been many examples of this, such as the ravages of the brown-tail and gypsy moths which were introduced into New England and of the San Jose scale which was introduced into California. There have been many other examples of the almost incredible power of multiplication of an animal or plant when taken into a new environment, removed from conditions which held it in check, as the introduction of the mongoose into Jamaica, the rabbit into Australia, the thistle into New South Wales and the water-plant chara into England.

It is very difficult to say, but it seems as though there is an increasing unevenness in the distribution of wealth, an increase in the number of persons who live at the expense of the laboring cla.s.s.

Ma.s.s labor, effective though it be, makes it easier to divert the proceeds of labor from the laborers. The evidence of this is seen in the increase in number and the prosperity of those pursuits which purvey to luxury, as the automobile industry and the florists' trade and the greatly increased scope and activity of the social game. On the other hand, there is an increase in the number of people who are to a greater or less extent dependent upon extraneous aid, evinced among other ways by the increase in the asylum populations. Both these conditions, wealth and poverty, are important disease factors.

Tuberculosis is now a disease of the proletariat chiefly. The measures both of prevention and cure can be and are carried out by the well-to-do, but the disease must remain where there are the conditions of the slums. Of all the conditions favoring infant mortality poverty comes first. In Erfurt, a small city of Germany, of one thousand infants born in each of the different cla.s.ses, there died of the illegitimate children three hundren and fifty-two; of those of the laboring cla.s.s, three hundred and five; of those in the medium station (official cla.s.s largely), one hundred and seventy-three; of those in higher station, eighty-nine. The same relation of infant mortality to poverty becomes apparent when estimated in other ways. In Berlin, with an average infant mortality of one hundred and ninety-six per thousand, the deaths in the best districts of the city were fifty-two and in the poorer quarters four hundred and twenty. The effect of poverty is seen particularly in the bottle-fed infants; with natural nursing the child of poverty has almost as good a chance as the child of wealth. From reasons which are almost self-evident, the mortality in illegitimate infants is almost double that of the legitimate. The greater infant mortality in poverty is due to the more numerous children preventing individual care, the separation of the mother from the nursing child in consequence of the demand made upon her earning capacity, and the decline in breast nursing. Wealth is on the whole more advantageous from the narrow point of view of disease than is poverty, but if we regard its influence on the race its advantages are not so evident. Nothing can be worse for a race than that it should die out, and wealthy families have never reproduced themselves.

Conditions always tending to destruction are a necessary part of the environment of poverty; wealth voluntarily creates these conditions, and chiefly by the pernicious influence of its amus.e.m.e.nts on the young.

A new and in many respects a n.o.bler conception of medicine has been developed. Formerly medical practice was almost exclusively a personal service to the sick individual, and measures looking toward the general relief of disease and its prevention received scanty consideration. The idea of a wider service to the city, to the state, to the nation, to humanity rather than the personal service to the individual, is becoming dominant in medicine. This is seen in the establishment of laboratories by boards of health in cities and states in which knowledge obtained by exact investigations can be made of direct service to the people; in the medical inspection of schools and factories; in promulgating laws directed against conditions which affect health, in the extension of hospitals, and in divers other ways. The idea of public service and of returning to the people in an effective way some of the results of their labor also underlies the large donations which have been given for the creation of special laboratories and inst.i.tutes in which, through research, greater knowledge of disease may be obtained and made available. The researches which have been made on the nutrition of man and the nutritive value of different foods are of great importance, and this knowledge has not yet begun to be applied as it should be.

There seems to be a balance maintained between the restriction of disease by prevention and the increased influence of social conditions which are in themselves factors of disease. Preventive medicine seems to have made possible, by restricting their harmful influence, the increase in industrialism, in urban life, and in the intercommunications of peoples. The most important aid in the future to the influence of preventive medicine must be the education of the people so that the conditions of disease, the intrinsic and the extrinsic causes and the manner in which these act, shall all become a part of general knowledge, and the sympathy of the people with health legislation and their active a.s.sistance in carrying out measures of prevention may be obtained. The effect of social conditions on disease must become more generally recognized.

GLOSSARY

ATROPHY--A condition of imperfect nutrition producing diminution in size and loss of function of parts.

BERTILLON--A French anthropologist who devised a system of measurements of the human body for purposes of identification.

BLOOD-PLASMA--The fluid of the blood.

CELL--The unit of living matter. Living things may be unicellular or composed of a mult.i.tude of cells which are interdependent. The general ma.s.s of material forming the cell is termed cytoplasm. In this there is a differentiated area termed nucleus which governs the multiplication of cells. In the nucleus is a material termed chromatin which bears the factors of heredity.

CHEMOTROPISM--The influence of chemical substances in directing the movement of organisms.

EXUDATE--The material which pa.s.ses from the blood into an injured part and causes the swelling.