4i8 



NATURE 



{March 28, 1878 



Anatomy, the whole of which appear to have been 

 destroyed when his house was plundered with the con- 

 nivance, if not by order, of the Parliament, during his 

 absence from London with the King. 



Of the " Exercitatio de Motu Cordis et Sanguinis," I 

 have treated so fully elsewhere ' on a recent occasion, that 

 I will again not touch upon the subject except so far as to 

 repeat that, in my judgment, Harvey is entitled, beyond 

 dispute, to be regarded as the sole discoverer of the 

 circulation of the blood, and of the method of its pro- 

 pulsion by the heart. 



The story of the extraction of the manuscript of the 

 " Exercitationes de Generatione " from Harvey is well told 

 by Ent, who undertook the charge of seeing the work 

 through the press ; a task of no small magnitude if we 

 consider the superlative badness of the extant specime»s 

 of Harvey's handwriting. 



The preface contains a singularly interesting disquisi- 

 tion on scientific method ; and, among other observations 

 the following, which is, perhaps, the weightiest in small 

 compass ever laid before the student of physical science. 



"For those who read the words of authors, and to whom 

 impressions of their own senses do not represent the 

 things signified by those words, conceive, not true ideas, 

 but falsce eidola and inane phantoms ; whence they fill 

 their minds with shadows and chimasras, and their whole 

 theory (which they think to be science) represents but a 

 waking dream or a sick man's delirium." 



As in the case of the circulation of the blood, the 

 scientific opinions of the day respecting the conditions of 

 generation and the embryogenic process had descended 

 from the Greeks. No one doubted that a large proportion 

 of the lower forms of Hfe owed their origin to equivocal 

 or spontaneous generation, or, as it is now termed, abio- 

 genesis ; and, with respect to sexual generation, it was 

 believed that the embryo originated at the time of sexual 

 union, by the combination of two substances poured out 

 ad hoc, the one being derived from the female, the other 

 from the male parent. In this opinion both Aristotle and 

 the Medici, following Galen, agreed ; but they differed in 

 the view which they took as to the nature and function 

 of the two sexual elements. According to Aristotle, the 

 female supplied merely the material of the embryo, by the 

 excretion of a substance which he regarded as the purest 

 part of the catamenial blood ; this was coagulated, and 

 endov/ed with the faculty of developing into an organism, 

 by the spermatic fluid, of the male. The Medici, on the 

 other hand, considered that the female produced a true 

 spermatic fluid, analogous to that of the male, and having 

 an equal formative energy ; and indeed, that the sex of 

 the embryo was determined by the predominance of the 

 one or the other spermatic fluid. 



As regards the embryogenic process itself, the Greeks 

 had studied the development of the chick, and had learned 

 somewhat respecting the foetal state of viviparous animals ; 

 while, since the revival of learning, several important 

 embryological investigations had been undertaken. Of 

 these the most notable were those of Aldrovandus, of 

 Goiter, of Harvey's master, Fabricius of Aquapendente, of 

 Veshng,and of Parisanus, on the development of the chick. 

 Fabricius' treatise, " De Ovo et PuUo," was accompanied 



• "Wi\\\a.m'iia.t\ey," Forinig/Uly Review, February i, 1878. 



by figures of the stages of development, which, for the 

 time, must be termed very good ; and it served Harvey 

 as a sort of text-book, to which he constantly refers. 



The " Exercitationes " show no advance on the know- 

 ledge of the ancients respecting the conditions of genera- 

 tion. Innumerable passages show that Harvey believed, 

 as firmly as his predecessors and contemporaries did, in 

 equivocal generation,' The persistent ascription to Harvey 

 of the contrary opinion is simply astounding, and can 

 only be explained on the supposition that those who quote 

 what they are pleased to call "Harvey's aphorism," "Omne 

 Vivum ex Ovo," against the holders of the doctrine of 

 spontaneous generation, have never read the works of their 

 authority. 



I cannot discover the exact phrase " omne vivum ex 

 ovo " anywhere in Harvey's works, though it is true that 

 the sense of the words is expressed by him over and over 

 again. But the context shows his meaning to be, not the 

 assertion of the doctrine of biogenesis ; but simply a 

 declaration that, in whatever way a living being is gene- 

 rated, the nature which it at first possesses is that of an 

 tgg. And what Harvey wants to impress, by the frequent 

 iteration of his opinion on this subject, is the difference 

 between his view, that a germ is something which comes 

 into existence more or less as a unit and has an indi- 

 viduality of its own, and that of his predecessors, who held 

 that it is formed by the coalescence of separate entities. 

 Nevertheless, there is an indication that Harvey was on 

 the right track in respect of the question of spontaneous 

 generation ; and that, if his papers on the generation of 

 insects had not been destroyed, he might have anticipated 

 Redi ; for the forty-first exercise contains the following 

 remarkable passage : — 



" But on these matters generally we shall have much to 

 say, when we shall show that many animals, especially 

 insects, take their origin and are generated from elements 

 and seeds so small as to escape observation (like atoms 

 floating in the air), which are scattered and dispersed 

 hither and thither by the winds ; yet these animals are 

 supposed to arise spontaneously, or from putrefaction, 

 because their germs are nowhere to be found." 



It was exactly this thesis that Redi adopted and proved 

 to demonstration, seventeen years afterwards, and there- 

 fore long before Harvey's death ; and it is by following 

 up the same line of argument that modern investigators 

 have deprived abiogenesis of its last supposed experi- 

 mental evidence. In whatever way, however, the germ 

 of a plant or of an animal is produced it is the equivalent 

 of an egg, and what Harvey means by an egg is clearly 

 shown, in the following as in many other passages : — 



" In the generation of all living things (as we have said) 

 this is established, that they arise from some primordium 

 (primordio aliquo) which contains not only the matter but 

 the power of generation ; and is, therefore, that out of 

 which and from which the thing generated takes its 

 origin. Such a primordium in animals (whether they 

 proceed from parents, or arise spontaneously or out of 

 putrefaction) is a humour contained in a membrane of 

 some kind, or shell ; in fact, a homogeneous body (corpus 

 nempe similare) possessing life, either actually or poten- 



' I pointed this out twenty years ago in my ' ' Lectures on General 

 Natural History," published in the Medical Times and Gazette. Take 

 one passage out of fifty that might be cited : '_' Atque etiam terra sua 

 sponte plurima general sine semine" (Exercit, xxix.). M. Pouchet might 

 hive taken this sentence for a motto. 



