Medical Investigation in Seventeenth Century England Part 1

Medical Investigation in Seventeenth Century England.

by Charles W. Bodemer and Lester S. King.

_Foreword_

Although the collection of scientific literature in the Clark Library has already served as the background for a number of seminars, in the most recent of them the literature of embryology and the medical aspects of Robert Boyle's thought were subjected to a first and expert examination. Charles W. Bodemer, of the Division of Biomedical History, School of Medicine, University of Was.h.i.+ngton, evaluated the embryological ideas of that remarkable group of inquiring Englishmen, Sir Kenelm Digby, Nathaniel Highmore, William Harvey, and Sir Thomas Browne. Lester S. King, Senior Editor of the _Journal of the American Medical a.s.sociation_, dealt with the medical side of Robert Boyle's writings, the collection of which const.i.tutes one of the chief glories of the Clark Library. It was a happy marriage of subject matter and library's wealth, the former a noteworthy oral presentation, the latter a spectacular exhibit. As usual, and of necessity, the audience was restricted in size, far smaller in numbers than all those who are now able to enjoy the presentations in their present, printed form.

C. D. O'MALLEY

_Professor of Medical History, UCLA_

I

_Embryological Thought in Seventeenth Century England_

CHARLES W. BODEMER

To discuss embryological thought in seventeenth-century England is to discuss the main currents in embryological thought at a time when those currents were both numerous and s.h.i.+fting. Like every other period, the seventeenth century was one of transition. It was an era of explosive growth in scientific ideas and techniques, suffused with a creative urge engendered by new philosophical insights and the excitement of discovery. During the seventeenth century, the ideas relating to the generation and development of organisms were quite diverse, and there were seldom criteria other than enthusiasm or philosophical predilection to distinguish the fanciful from the feasible. Applying a well-known phrase from another time to seventeenth-century embryological theory, "It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness."[1]

Embryology underwent some very significant changes during the seventeenth century. At the beginning of the century, embryology was descriptive and clearly directed toward morphological goals; by the end of the century, a dynamic, more physiological att.i.tude was apparent, and theories of development derived from an entirely different philosophic base. During this time, English investigators contributed much, some of ephemeral, some of lasting importance to the development of embryology.

For this discussion, we will divide the seventeenth century into three overlapping, but generally distinct, periods; and, without pretence of presenting an exhaustive exposition, we will concentrate upon the concepts and directions of change characteristic of each period, with primary reference to those individuals who best reveal the character of seventeenth-century English embryology.

An understanding of the characteristics of embryological thought at the beginning of the seventeenth century may enhance appreciation of later developments. During the latter part of the sixteenth century, the study of embryology was, for obvious reasons, most often considered within the province of anatomy and obstetrics. From Bergengario da Capri to Jean Riolan the Younger, study of the fetus was recommended as an adjunct of these subjects, and it required investigation by direct observation, as decreed by the "restorers" of anatomy. Embryonic development was, however, also studied independently of other disciplines by a smaller group of individuals, and the study of chick development by Aldrovandus, Coiter, and Fabricius ab Aquapendente laid the basic groundwork of descriptive embryology. In either case, during the last half of the sixteenth century the attempt of the embryologist to break with the traditions of the past was overt, although consistently unsuccessful.

When dealing with the fetus, the investigators of this period were, almost to a man, Galenists influenced to varying degrees by Hippocrates, Aristotle, and Avicenna. Each felt compelled to challenge the immediate authority, and yet their intellectual isolation from the past was incomplete, and their views on embryogeny corresponded with more often than they differed from those of the person they railed against.

Embryology emerged as a distinct scientific discipline during the last half of the sixteenth century and early years of the seventeenth century as a result of the aforementioned investigations of Aldrovandus, Coiter, and Fabricius. Concerned with description and depiction of the anatomy of the embryo, they established a period of macro-iconography in embryology. The macro-iconographic era was empirical and based upon first-hand observation; it was concerned more with the facts than with the theories of development. This empiricism existed in compet.i.tion with a declining, richly vitalistic Aristotelian rationalism which had virtually eliminated empiricism during the scholastic period. However, the decline of this vitalistic rationalism coincided with the rise of a mechanistic rationalism which had its roots in ancient Greek atomistic theories of matter. The empiricism comprising the _leitmotif_ of the macro-iconographic movement then became blended with, or, more often, submerged within, the new variety of rationalism; hence, mechanistic rationalism, divorced entirely or virtually from empiricism, characterizes embryology during the first half of the seventeenth century. It is a particularly vigorous strain of seventeenth-century English embryological thought, well ill.u.s.trated in the writings of that English man of affairs, Sir Kenelm Digby.

Digby, whose name, according to one biographer, "is almost synonymous with genius and eccentricity,"[2] could claim our attention not only as a scientist of talent, but also as a statesman, soldier, pirate, lover, and a Roman Catholic possessed of sufficient piety and naked courage to attempt the conversion of Oliver Cromwell. Like his father, who was hanged for partic.i.p.ation in the Gunpowder Plot, Digby was a political creature, and during the Civil War he was imprisoned for several years.

When freed, Digby left England to settle in France. Spending much time at the court of the Queen Dowager, who had been instrumental in securing his release, and exposed to the vigorous intellectual currents of Paris and Montpellier, Digby labored upon a treatise of greater scientific substance and merit than his more famous work on "the powder of sympathy." Published in 1644 under the t.i.tle _Two Treatises, in the One of Which, The Nature of Bodies; in the Other, the Nature of Mans Soule; is Looked_ _into, in Way of Discovery of the Immortality of Reasonable Soules_, the book consists of a highly individual survey of the entire realms of metaphysics, physics, and biology.

Digby's cannons were aimed at scholasticism, which, despite "greatly exaggerated" reports, did not die with the Middle Ages. The spirit of scholasticism was alive in many quarters well into the seventeenth century, and although many scholars worked in pursuit of original knowledge, they did not always disturb the scholastic philosophic basis from which their work derived. For example, in his impressive _De formato foetu_, published in 1604, when Sir Kenelm Digby was one year old, Fabricius all too often submerges a substantial body of observations within a dense tangle of philosophical discussion. Thus, in the same treatise that contains the first ill.u.s.trations and commendably accurate descriptions of the daily progress of the chick's development, Fabricius devotes an inordinate amount of s.p.a.ce to tedious discussions of material and efficient causes in development, emphasizing thereby the supremacy of the logical framework to the observations. In 1620, Digby's last year of study at Oxford University, Fienus published a work, _De Formatrice Foetus_, designed to demonstrate that the human embryo receives the rational soul on the third day after conception and to discuss at length such subjects as the efficient cause of embryogeny and the proposition that the conformation of the fetus is a vital, not a natural, action. Various expressions of Aristotelian and scholastic biology were clearly abroad during the first half of the seventeenth century, and there is reason, then, for Digby's attack upon Aristotelian ideas of form and matter and of the persistence of "qualities" in physics and "faculties" in biology.

Expressing his disdain of word-spinning, Digby attempts to explain all phenomena by two "virtues" only, rarity and density working by local motion. In discussing embryonic development, Digby writes, "...our maine question shall be, Whether they be framed entirely at once; or successively, one part after another? And, if this later way, which part first?"[3] Toward this end, Digby makes some direct observations upon the development of the chick embryo, incubating the eggs so that the "creatures ... might be continually in our power to observe in them the course of nature every day and houre."[4] His description of chick development is of epigenetic bent:

...you may lay severall egges to hatch; and by breaking them at severall ages you may distinctly observe every hourely mutation in them, if you please. The first will bee, that on one side you shall find a great resplendent clearnesse in the white. After a while, a little spott of red matter like bload, will appeare in the middest of that clearnesse fastened to the yolke: which will have a motion of opening and shutting; so as sometimes you will see it, and straight againe it will vanish from your sight; and indeede att the first it is so litle, that you can not see it, but by the motion of it; for att every pulse, as it openeth, you may see it, and immediately againe, it shutteth in such sort, as it is not to be discerned. From this red specke, after a while there will streame out, a number of litle (almost imperceptible) red veines. Att the end of some of which, in time there will be gathered together, a knotte of matter which by litle and litle, will take the forme of a head; and you will ere long beginne to discerne eyes and a beake in it. All this while the first red spott of blood, groweth bigger and solider; till att the length, it becometh a fleshy substance; and by its figure, may easily be discerned to be the hart: which as yet hath no other enclosure but the substance of the egge. But by litle and litle the rest of the body of an animal is framed out of those red veines which streame out all aboute from the hart. And in processe of time, that body incloseth the hart within it by the chest, which groweth over on both sides, and in the end meeteth, and closeth it selfe fast together. After which this litle creature soone filleth the sh.e.l.l, by converting into severall partes of it selfe all the substance of the egge. And then growing weary of so straight an habitation, it breaketh prison, and cometh out, a perfectly formed chicken.[5]

Despite this observational effort, Digby's experience with the embryo is quite limited, and his theory of development relates more to his philosophical stance than to the facts of development. Indeed, the theory he propounds is not necessarily consistent. On the one hand, it posits a strictly mechanistic epigenesis, and on the other hand, it incorporates the notion of "specificall vertues drawne by the bloud in its iterated courses, by its circular motion, through all the severall partes of the parents body."[6] Digby rejects an internal agent, entelechy, or the Aristotelian formal and efficient causes. Similarly, he disposes of the idea that the embryonic parts derive from some part of each part of the parent's body or an a.s.semblage of parts. This possibility is eliminated, he contends, by the occurrence of spontaneous generation. If a collection of parts was necessary, he asks, "how could vermine breed out of living bodies, or out of corruption?... How could froggs be ingendered in the ayre?"[7] Generation in plants and animals must, then, according to Digby, proceed from the action of an external agent, effecting the proper mingling of the rare and dense bodies with one another, upon a h.o.m.ogeneous substance and converting it into an increasingly heterogeneous substance. "Generation," he says,

is not made by aggregation of like partes to presupposed like ones: nor by a specificall worker within; but by the compounding of a seminary matter, with the juice which accreweth to it from without, and with the streames of circ.u.mstant bodies; which by an ordinary course of nature, are regularly imbibed in it by degrees; and which att every degree do change it into a different thing.[8]

Digby argues that the animal is made of the juices that later nourish it, that the embryo is generated from superfluous nourishment coming from all parts of the parent body and containing "after some sort, the perfection of the whole living creature."[9] Then, through digestion and other degrees of heat and moisture, the superfluous nourishment becomes an h.o.m.ogeneous body, which is then changed by successive transformations into an animal.

Digby is frankly deterministic in his description of embryonic development:

Take a beane, or any other seede, and putt it into the earth, and lett water fall upon it; can it then choose but that the beane must swell? The beane swelling, can it choose but breake the skinne? The skinne broken can it choose (by reason of the heate that is in it) but push out more matter, and do that action which we may call germinating.... Now if all this orderly succession of mutations be necessarily made in a beane, by force of sundry circ.u.mstances and externall accidents; why may it not be conceived that the like is also done in sensible creatures; but in a more perfect manner....

Surely the progresse we have sett downe is much more reasonable, then to conceive that in the meale of the beane, are contained in litle, severall similar substances.... Or, that in the seede of the male, there is already in act, the substance of flesh, of bone, of sinewes, of veines, and the rest of those severall similar partes which are found in the body of an animall; and that they are but extended to their due magnitude, by the humidity drawne from the mother, without receiving any substantiall mutation from what they were originally in the seede. Lett us then confidently conclude, that all generation is made of a fitting, but remote, h.o.m.ogeneall compounded substance: upon which, outward Agents working in the due course of nature, do change it into an other substance, quite different from the first, and do make it lesse h.o.m.ogeneall then the first was. And other circ.u.mstances and agents, do change this second into a thirde; that thirde, into a fourth; and so onwardes, by successive mutations (that still make every new thing become lesse h.o.m.ogeneall, then the former was, according to the nature of heate, mingling more and more different bodies together) untill that substance be produced, which we consider in the periode of all these mutations....[10]

Digby thus makes a good statement of epigenetic development. He attempts, without success, a physiochemical explanation of the mechanisms of development, finally admitting:

I persuade my selfe it appeareth evident enough, that to effect this worke of generation, there needeth not be supposed a forming vertue ... of an unknowne power and operation.... Yet, in discourse, for conveniency and shortnesse of expression we shall not quite banish that terme from all commerce with us; so that what we meane by it, be rightly understood; which is, the complexe, a.s.semblement, or chayne of all the causes, that concurre to produce this effect; as they are sett on foote, to this end by the great Architect and Moderatour of them, G.o.d Almighty, whose instrument Nature is.[11]

Digby's general theory thus represents a strange mixture of epigenesis and pangenesis, and is not entirely devoid of "virtues." It is, however, a bold attempt to explain embryonic development in terms commensurate with his time, and it embodies the same optimistic belief that the mechanism of embryogenesis lay accessible to man's reason and logical faculties that similarly led Descartes and Ga.s.sendi to comprehensive interpretations of embryonic development comprising a maximum of logic and minimum of observations.

The traditionalist reaction to the attack upon treasured and intellectually comfortable interpretations of development was not slow to set in. A year after the appearance of Digby's _Nature of Bodies_, Alexander Ross published a treatise with a t.i.tle indicating its goals and content: _The Philosophicall Touch-Stone; or Observations upon Sir Kenelm Digbie's Discourses of the nature of Bodies, and of the reasonable Soule: In which his erroneous Paradoxes are refuted, the Truth, and Aristotelian Philosophy vindicated, the immortality of mans Soule briefly, but sufficiently proved_.[12] Ross supports the Galenist tradition that the liver, not, as Digby claimed, the heart, forms first in development. It can be no other way, he says, since the blood is the source of nourishment and the liver is necessary for formation of the blood. Furthermore, he contends, "the seed is no part of the ... aliment of the body ... the seed is the quintessence of the blood."[13] Ross is an epigeneticist, to be sure, but so was Aristotle, and Ross prefers to maintain the supremacy of logic and the concepts of the Aristotelian tradition as a guide to the interpretation of development.

In 1651, Nathaniel Highmore, a physician at Sherborne in Dorset, published _The History of Generation_, which, he informs us, is an answer to the opinions expressed by Digby in _The Nature of Bodies_.

Highmore's book is an important one in the history of embryology, since it is the first treatment of embryogeny from the atomistic viewpoint and because it contains the first published observations based upon microscopic examination of the chick blastoderm. Admittedly, the drawings ill.u.s.trating Highmore's observations upon generation are, to use a word often applied to modern art, "interesting," but they do derive from actual observations of developing plant and animal embryos.

His observations on the developing chick embryo are quite full, complete, and exact, and he also records some interesting facts regarding development of plant seeds.

Highmore's theory of development appears to have emerged directly out of his observations of development. In this sense, his theory rests upon a more solid base than does the developmental theory of Digby. His theory is a mixture of vitalism and atomism, designed to eliminate the "fortune and chance"[14] resident in Digby's concept. "Generation," he says,

...is performed by parts selected from the generators, retaining in them the substance, forms, properties, and operations of the parts of the generators, from whence they were extracted: and this Quintessence or Magistery is called the seed. By which the Individuals of every Species are multiplied...

From this, All Creatures take their beginning; some laying up the like matter, for further procreation of the same Species.

In others, some diffus'd Atomes of this extract, shrinking themselves into some retired parts of the Matter; become as it were lost, in a wilderness of other confused seeds; and there sleep, till by a discerning corruption they are set at liberty, to execute their own functions. Hence it is, that so many swarms of living Creatures are from the corruption of others brought forth: From our own flesh, from other Animals, from Wood, nay, from everything putrified, these imprisoned seminal principles are muster'd forth, and oftentimes having obtained their freedom, by a kinde of revenge feed on their prison; and devour that which preserv'd them from being scatter'd.[15] Accounting thus for s.e.xual and spontaneous generation, Highmore defines two types of seminal atoms in the seed--"Material Atomes, animated and directed by a spiritual form, proper to that species whose the seed is; and given to such matter at the creation to distinguish it from other matters, and to make it such a Creature as it is."[16] The seminal atoms come from all parts of the body, the spiritual atoms from the male, and the material atoms from the female. The atoms of Democritus are thus trans.m.u.ted into the "substantial forms" and endowed either with the efficient cause of Aristotle or, permitted to remain material, with Aristotle's material cause. According to Highmore, the atoms are circulated in the blood, which is a "tincture extracted from those things we eat," and these various atoms retain their formal ident.i.ty despite corruption. The t.e.s.t.i.c.l.es abstract some spiritual atoms belonging to each part and, "As the parts belonging to every particle of the Eye, the Ear, the Heart, the Liver, etc. which should in nutrition, have been added ... to every one of these parts, are compendiously, and exactly extracted from the blood, pa.s.sing through the body of the t.e.s.t.i.c.l.es." Being here "cohobated and reposited in a tenacious matter," the particles finally pa.s.s out of the testes.[17] A similar extraction of the female seed occurs in the ovaries. The female seed

...containing the same particles, but cruder and lesse digested, from a cruder matter, by lesse perfect Organs, is left more terrene, furnished with more material parts; which being united in the womb, with the spiritual particles of the masculine seed; everyone being rightly, according to his proper place, disposed and ordered with the other; fixes and conjoynes those spiritual Atomes, that they still afterwards remain in that posture they are placed in.[18]

The theories of development promulgated by Digby and Highmore reveal the chief formulations of mechanistic rationalism, more or less free of empiricism, that were emerging as the vitalism of the sixteenth and seventeenth centuries waned. There was little new in these theories: both Digby's and Highmore's theories included different combinations of elements of ancient lineage. Digby's concept was essentially free of vitalistic coloring; akin to the embryological efforts of Descartes in its virtual independence from observations of the developing embryo, it was similarly vulnerable to Voltaire's criticism of Descartes, that he sought to interpret, rather than study, Nature. This criticism is not so applicable to Highmore, whose theory of development is more vitalistic than Digby's, and is more akin to the concepts developed by Ga.s.sendi than those of Descartes. Highmore had experience with the embryo itself, and his actual contribution as an observer of development, although hardly epochal, is worthy of note. But despite this empirical base, Highmore has final recourse to a hypothesis blending many ancient ideas and subst.i.tuting the Aristotelian material and efficient causes for the "fortune and chance" he objected to in Digby's hypothesis. It was _not_ easy in the seventeenth century to avoid falling back upon some variety of cause or force.

In 1651, about two months before publication of Highmore's _History of Generation_, a work appeared which marks another period in seventeenth-century English embryology. William Harvey, _De Motu Cordis_ almost a quarter of a century behind him, now published _De Generatione Animalium_, the work he said was calculated "to throw still greater light upon natural philosophy."[19] This book is, perhaps, not as well known as Harvey's treatise demonstrating circulation of the blood, but it is an important work in the history of embryology and it occupies a prominent position in the body of English embryological literature.

In _De Generatione_, Harvey provides a thorough and quite accurate account of the development of the chick embryo, which, in particular, clarified that the chalazae, those twisted skeins of alb.u.men at either end of the yolk, were not, as generally believed, the developing embryo, and he demonstrated that the cicatricula (blastoderm) was the point of origin of the embryo. The famous frontispiece of the treatise shows Zeus holding an egg, from which issue animals of various kinds. On the egg is written _Ex ovo omnia_, a legend since trans.m.u.ted to the epigram _Omne vivum ex ovo_. The legend ill.u.s.trates Harvey's princ.i.p.al theme, repeated constantly throughout the text, "that all animals were in some sort produced from eggs."[20]

If Harvey made no contribution beyond emphasizing the origin of animals from eggs, he would deserve a prominent place in the history of embryology. But the work is also significant in its espousal of epigenesis, and, supported as his argument was by observation and logic, it became the prime formulation of that concept of development during the seventeenth and eighteenth centuries. His statement of epigenetic development is clear:

In the egg ... there is no distinct part or prepared matter present, from which the fetus is formed ... an animal which is created by epigenesis attracts, prepares, elaborates, and makes use of the material, all at the same time; the processes of formation and growth are simultaneous ... all its parts are not fas.h.i.+oned simultaneously, but emerge in their due succession and order ...

Those parts, I say, are not made similar by any successive union of dissimilar and heterogeneous elements, but spring out of a similar material through the process of generation, have their different elements a.s.signed to them by the same process, and are made dissimilar ... all its parts are formed, nourished, and augmented out of the same material.[21]

Actually, Harvey's exposition of epigenesis, albeit clear, is not totally impressive, since it is largely a reflection of Aristotle's influence. The main importance of Harvey's vigorous and cogent defense of epigenesis is that it provided some kind of counterbalance to the increasingly dominant preformationist interpretations of embryonic development.

Harvey did not break with Aristotelianism; on the contrary, he lent considerable authority to it. Unable to escape the past, he was not completely objective in his study of generation. Everywhere the pages of his book reveal his indebtedness to past authorities. Robert Willis, who provided the 1847 translation of _De Generatione_, expresses this well:

[Harvey] ... begins by putting himself in some sort of harness of Aristotle, and taking the bit of Fabricius between his teeth; and then, either a.s.suming the ideas of the former as premises, or those of the latter as topics of discussion or dissent, he labours on endeavouring to find Nature in harmony with the Stagyrite, or at variance with the professor of Padua--for, in spite of many expressions of respect and deference for his old master, Harvey evidently delights to find Fabricius in the wrong. Finally, so possessed is he by scholastic ideas, that he winds up some of his opinions upon animal reproduction by presenting them in the shape of logical syllogisms.[22]

Even Harvey's concept of the egg reveals a strong Aristotelian bias.

Actually, Harvey attained to his conclusion that all animals derive from eggs by a.s.suming that