METHODS OF PHYSIOLOGICAL RESEARCH 15 



The chief result of this undertaking found expression in the 

 inauguration of a peculiar school founded upon Borelli's doctrine, 

 the iatromechanical school (called also iatrophysical and iatromathe- 

 matical), which played a considerable role in the further develop- 

 ment of physiology, since it endeavoured to explain other vital 

 phenomena of the animal body upon purely physical principles. 

 At the same time, some of Borelli's followers, especially Glisson, 

 by regarding contractility as a property residing within muscle- 

 substance itself, became the precursors of the later doctrine of the 

 irritability of muscle. 



Almost contemporaneous with the founding of the iatrophysical 

 .school there arose another school, the iatrochemical, which for a 

 time flourished by the side of the former. Its founder was Sylvius 

 (1614-1672). Dissatisfied with the narrowness of the iatro- 

 physicists, but recognising the importance of their principle in 

 explaining vital phenomena, Sylvius emphasized the chemical side 

 in addition to the physical, and in accordance with this elaborated 

 chiefly the physiology of digestion and respiration by extending 

 van Helmont's doctrine of the ferments. In the theory of respira- 

 tion also, Mayow (1645-1679) expressed very pertinent thoughts 

 upon the analogy between respiration and combustion. 



At this time physiology derived considerable assistance, the 

 value of wtjich for physiological investigation, however, has not 

 been completely taken advantage of even to the present day, from 

 the invention of the compound microscope and the microscopic 

 discoveries made by means of it by Leeuwenhoek (1632-1723), 

 Malpighi (1628-1694) and Swammerdamm (1637-1685). The 

 knowledge of the physiology of reproduction and development, 

 more than all else, was thus markedly advanced. The first micro- 

 scopic discoveries in this field naturally led to many excusable 

 errors. When, for example, aqueous infusions of decomposable sub- 

 stances were made and the appearance of Infusoria in immense 

 numbers was observed in them, spontaneous generation from lifeless 

 substances was believed to have taken place, contrary to Harvey's 

 dictum, " omne vivum ex ovo," but in accordance with Aristotle's 

 earlier assumption even for higher animals. On the other hand, 

 Harvey's dictum became the starting-point of important discoveries ; 

 for Malpighi followed the development of ova with the microscope, 

 while Leeuwenhoek's pupil, Ludwig van Hammen, discovered 

 spermatozoa, the importance of which Leeuwenhoek immediately 

 recognised. 



These and a great number of special physiological discoveries 

 which active investigation brought forth give to the period 

 of the seventeenth and eighteenth centuries after Harvey's 

 appearance the character of the dawn of exact investigation in 

 physiology, just as the influence of exact methods pervaded and 

 animated all science of that period. Yet, as is constantly happen- 



