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Prof. Rudolf Virchow. The Position of [Mar. 16, 



The influence of this one wonderful discovery of Harvey's on the 

 ideas of men of his time, and of his successors, was memorable. 



Among the men of his time the last support of Galenism disap- 

 peared with the proof of circulation ; upon his successors the com- 

 prehension of the causation of local processes dawned for the first time. 

 Very ancient and highly difficult problems, such as inflammation, 

 could now be attacked ; a goodly piece of life also became intelligible, 

 since one of the vital organs themselves could now be subjected to 

 experiment, and, to the astonishment of all, the action of this organ 

 showed itself to be an absolutely mechanical one. The revulsion of 

 thought was so complete that it has since become an almost insuper- 

 able difficulty to enter even in imagination into the ideas of the older 

 physicians, to whom the circulation of the blood was unknown. 



Nevertheless, in spite of such striking results, the craving of men 

 for more complete understanding remained unsatisfied. The action 

 of the living heart could be seen, but how did the heart live ? What 

 was this life, the action of which was so clearly visible ? In the 

 heart itself, the essence of life could not be recognised. 



Harvey turned his attention to another object ; he tried to observe 

 the very beginnings of life in the incubated egg of the fowl and 

 in the embryos of mammalian animals. He thereby soon arrived 

 at the question of the significance of the egg in general, and enun- 

 ciated the celebrated dictum, " Omne vivum ex ovo." Owing to the 

 more extensive researches of modern investigators, this dictum, as is 

 well known, proved too narrow for the whole animal kingdom, and 

 no longer exact when applied to plant life. Its validity for 

 the higher animals, on the other hand, cannot be questioned, and 

 it has formed one of the firm standpoints from which researches 

 on sexuality and on the propagation of life have proceeded. But 

 Harvey, on account of the defective character of his optical instru- 

 ments, was unable to see that which he was labouring to discover, 

 namely, the process of organisation as such, just as in former times he 

 had been unable to see the continuity of the capillary flow. This imper- 

 fection lasted for a long time afterwards ; and thus it happened that 

 even Albrecht von Haller and John Hunter considered the formation of 

 the area vasculosa in the incubated egg of the fowl as the commence- 

 ment of organisation, and indeed, as the type of organisation itself. 



I will return to this point later ; but I should like first to 

 draw your attention to a man whose importance for the farther 

 development of the doctrine of life has always appeared to me 

 to have been uncommonly great and highly significant, but who, 

 nevertheless, has sunk into unmerited oblivion, not only among pos- 

 terity in general, but also, I think I may be allowed to say, even 

 among his countrymen. I mean Francis Glisson, who was a 

 contemporary of Harvey, and whose works appeared almost simulta- 



