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HARVEY, WILLIAM. 



HARVEY, WILLIAM. 



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means of the veins, and that intended for the nutrition of the lunga 

 by the action of the right side of the heart. According to the same 

 doctrines the arteries were destined for the conveyance of the vital 

 spirits, which were formed in the left side of the heart from the air 

 and blood derived from the lungs. These vital spirits were supposed 

 to be taken in by the arteries during their diastole, and distributed 

 by them during their systole, whilst the vapours or fuligines, as they 

 are called by Harvey, were returned to the lungs by the action of the 

 left ventricle. Opinions did not agree upon the mode in which the 

 blood found its way to the left side of the heart, for whilst some sup- 

 posed that it was conveyed with the air from the lungs, others 

 maintained that it transuded by certain imaginary pores in the 

 septum between the ventricles. These opinions, it is evident, rested 

 more upon imagination than any careful observation of facts. Those 

 of Harvey, on the contrary, were drawn from the most accurate dis- 

 sections of dead and living animals, and supported by arguments 

 depending entirely upon the anatomical structure and obvious uses ol 

 the parts. The result of these observations is thus stated by him. 

 The heart has periods of action and of rest, but in warm-blooded 

 animals its motions are so rapid, that the different steps of them can- 

 not be distinguished. In cold-blooded animals they are more slow, 

 and in warm-blooded also after the examination of its action, by 

 opening the chest in a living animal, has been continued gome time. 

 During its action the heart is raised, and its point tilted forward so as 

 to strike against the parietes of the chest. It contracts in every direc- 

 tion, but more especially on its sides ; it also becomes harder, as 

 other muscles do during their contraction. In fishes and cold-blooded 

 animals the heart may be observed to become paler during its systole, 

 and assume a darker colour during its diastole. If a wound be made 

 in the ventricle, the blood is ejected from it during its contraction. 

 From these facts Harvey concluded that the essential action of the 

 heart is its systole, and not its diastole, as was supposed by physicians 

 before bis time, and that the result of this contraction is the expul- 

 sion of the blood into the pulmonary artery and aorta. The diastole 

 of the arteri s or pulse is synchronous with and caused by the pro- 

 pulsion of the blood during the systole of the ventricle, and is a 

 passive, and not, as was previously supposed, an active operation of 

 the vessels. If the motions of the heart be carefully observed for 

 some minute*, it will be seen first that the two auricles contract 

 simultaneously, and force the blood contained in them into the 

 ventricles ; and secondly, that the ventricles in their turn assume the 

 same action, and propel most of the blood into the pulmonary artery 

 and aorta, from which it is prevented from returning by the valves 

 situated at the entrance of those vessel*. The author next proceeds 

 to describe the manner in which the blood passes from the right to 

 the left side of the heart. 



During foetal life, says he, this is sufficiently evident. Fart of the 

 blood passes directly from the right to the left auricle through the 

 foramen ovale, whilst the rest is conveyed into the right ventricle, 

 and by its contraction forced into the pulmonary artery, and so 

 through the ductus arteriosua into the descending aorta ; for, as he 

 observed, the lungs do not admit of its passage through them in the 

 foetus. In the adult a new condition is introduced, namely the 

 lunction of the lungs, by which, as Harvey observed, the question 

 was so much obscured that physicians were uiiaole to give a correct 

 explanation of the phenomena. However, the consideration of the 

 obvious use of the valves of the pulmonary artery had led Qalen to 

 maintain that a portion of the blood contained in that vessel passed 

 through the lungs into the pulmonary veins, but this passage he sup- 

 posed to depend more upon the action of the lungs themselves thau 

 of the heart. Harvey carried out this argument still further, and 

 maintained from it that the whole of the blood which is propelled 

 from ttie right side passes through the lungs to the left side of the 

 heart. In like manner he showed that the blood is propelled from 

 the left ventricle into the arteries and so distributed to all parts of 

 the body. He next proceeded to give approximate calculations of the 

 quantity of blood which passes from the veins through the heart in a 

 givm time. This he showed to be so much more thau is required for 

 the nutrition, or can be supplied to the veins by the absorption of 

 alimentary substances, that the surplus must of necessity return 

 through the various tissues of the body to the veins again. He then 

 argued from the construction of the valves of the veins that the course 

 of the blood in them must be from the smaller to the larger divisions, 

 and thus to the heart again. The se views he still further confirmed by 

 reference to the now well-known effects of ligatures placed on a limb 

 with different degrees of tightness. If the ligature be so placed as 

 to compress the veins alone, they become swelled and tumid beyond 

 the ligature, and quite empty between it and the heart, whilst the 

 pulsations of the artery remain unaltered. If it be drawn a little 

 tighter the pulsations of the artery cease beyond, but are felt more 

 violent than usual just within the ligature. 



.Such is a brief abstract of the principal steps in this the greatest 

 and most original discovery in physiology, which was ao directly 

 opposed to all the previous notions of physicians, that its author 

 might well observe, "Adeo nova sunt et inuudita ut non solum ex 

 invulia quorundam metuam malum mini, Bed verear ne habeam 

 iuimicos omnes homines : tantuin consuetude aut semel imbibita 

 doctrma altisque denxa radicibus quasi altera natura, apud omnes 



valet, et antiquifcatis veneranda suspicio cogit." This anticipation 

 proved correct; for Harvey afterwards complained to one of his 

 friends, that his practice fell off considerably after the publication of 

 his treatise ' On the Circulation of the Blood,' and it is well known 

 that the doctrine was not received by any physician who was more 

 than forty years old. His opinions were violently opposed by Primi- 

 rosius, Parisanus, Hiolanus (1645), and others. Paiisanus was ably 

 refuted by his friend Dr. George Ent, Fellow of the College of 

 Physicians, and other advocates of Harvey's views appeared on the 

 Continent. The only man who was honoured by a reply from Harvey 

 himself was Riolanus, professor of anatomy in Paris, in answer to 

 whom he published two letters. In 1652 Harvey had the satisfac- 

 tion of seeing one of his early opponents, Plempius, professor at 

 Louvain, declare himself a convert to his opinions, and by his example 

 many more were induced to withdraw their opposition. lu the whole 

 of this controversy, says Sprengel (' Hist, of Med.,' sect, xii., c. 1), the 

 discretion and rare modesty of Harvey afford the best model for 

 naturalists and scientific writers. 



Harvey had been so much disgusted by the disputes in which he 

 was involved on the publication of his views on the circulation of the 

 blood that he had determined to publish nothing more, and it was only 

 at the earnest request of his friend Dr. Ent that he was induced to 

 allow his ' Exercitationes de Generatione ' to be printed. This work 

 consists partly of a commentary upon the writings of Aristotle and 

 Fabricus ab Aquapendente on the same subject, and partly of details 

 of his own observations and experiments. The earlier ' Exercitationes' 

 contain a description of the organs of generation in the common fowl, 

 of the formation of the egg and its extrusion from the body, and of 

 the use and nature of its various parts, as well as the changes which it 

 undergoes during the process of incubation. He then proceeds to enter 

 upon some discussions on the nature of the act of generation, and of 

 the degree in which the male and female respectively contribute to its 

 performance, in the course of which he examines the opinions of 

 Aristotle upon this abstruse subject, and advances some of his own. 

 The concluding treatises contain a description of the analogous 

 processes in the deer. 



Without venturing upon an abstract of the whole contents of these 

 papers, we shall endeavour to give some idea of the knowledge possessed 

 by Harvey, and especially of his own discoveries and additions to this 

 most interesting branch of physiology. He described the organs of 

 generation in the fowl : he observed that the vitellin or yoke is at first 

 in vascular connection with the parent, that this connection is after- 

 wards broken off, and that in its passage through the oviduct the 

 layers of albumen are added, and that before its final extrusion from 

 the body of the mother the hard shell was formed : he asserted that 

 all these parts, even the shell itself, are formed from the same sub- 

 stance under the influence of the assimilative power of the egg itself, 

 and are not mere secretions from the organs of the parent, as was 

 previously supposed : he was the first to describe accurately the two 

 layers of albumen, and to show that each is contained in its own proper 

 membrane : he was aware that the shell is porous, and admits of the 

 respiration of the chick through it : he described the cualazse at each 

 end of the egg, and showed that they exist in the uniuipregnated as 

 well as the impregnated egg; whereas it had been previously supposed, 

 and especially by his master Fabricius, that these parts represent the 

 germ from which the future chick was to be formed. The greatest 

 discovery however made by Harvey in this branch of physiology was 

 the use and importance of the ' cicatricula,' which he showed to be 

 the true germ in which all the future changes take place, and for the 

 increase and nutrition of which all the other parts of the egg are 

 destined. He showed that it is present before the yoke has left the 

 ovary, and pointed out the error of Fabricua, who considered it the 

 remains of the pedicle by which tbe vitellus was attached to the ovary : 

 he was aware that eggs occasionally contain a double yolk, and asserted 

 that twins are produced from such eggs, but that they do not survive. 

 The fifteenth and seven following ' Exercitationes' contain a description 

 of the changes which the egg undergoes from the first to the fourteenth 

 day of incubation. H described minutely the changes which take 

 place in tbe cicatricula at the end of the second day. The>e observa- 

 tions appear to have been quite original : " At this time it attains the 

 size of the finger-nail nearly ; two and sometimes three concentric 

 layers may be observed in it. The central one is the most transparent 

 of the two. In the middle of it is a white speck, which from its 

 appearance may be compared to a cataract in the centre of the pupil 

 of the eye. During this day the central layer especially enlarges and 

 entrenches upon the external one." This description appears to accord 

 with that of the ' area pellucida,' to which so much importance is 

 attached by later writers on this subject. " At the end of the third 

 day a pulsating spot may be observed in the centre of the ' cicatricula,' 

 which forms the rudiment of the future heart." He observed that the 

 pulsations may be called forth afresh, when languid or intermitted, 

 by the employment of various stimuli : he showed that the liver is 

 formed round the umbilical vein, but he does not seem to have been 

 aware that the liver, as well as all the other glands whose ducts com- 

 municate with the intestinal canal, is a prolongation or growth from 

 the intestinal sac : he described five umbilical vessels, of which three 

 are veins and two arteries, one of the veins being distributed to the 

 albumen, the other four vessels to the vitellus. The first-mentioned 



