Makch 9, 1900.] 



SCIENCE. 



365 



Both left Konigsberg for wider fields, von 

 Baer, however, to largely lay aside his em- 

 bryological researches, the other to extend 

 and correlate his. An interesting difference 

 between the two embryologists is this, that 

 von Baer had completed his most important 

 work when he was scarcely over forty years 

 of age, while von Kupffer had not begun his 

 best known work until he was over sixty. 

 A further difference is that Kupffer has held 

 fast to the early themes of his research. 

 Von Baer lived until his eighty-sixth year ; 

 von Kupffer has entered his eighth decade 

 with every prospect of many years of active 

 work. 



Von Kupffer has devoted forty- five years 

 to his researches. And these he has em- 

 bodied in upwards of fifty memoirs. The 

 number seems relatively small — the bibli- 

 ography of von Baer is six times as great 

 — but this is explained by the fact that the 

 papers are mainly of a critical character 

 and are the fruit of intricate and time- 

 consuming studies, just as von Baer's 

 ' Entwicklungsgeschichte der Thiere ' was 

 the outcome of no less than nine years' of 

 assiduous labor. 



The writings of von Kupffer deal in the 

 main with problems in special fields of em- 

 bryology. A number of his well-known 

 papers are contributions to histology, and 

 there are several dealing with craniology, 

 including the memoirs on the skull of his 

 illustrious predecessor in Konigsberg, Im- 

 manuel Kant. 



The histological work of von Kupffer ex- 

 tends over a wide range of subjects. To 

 cytologists he is known as a pioneer in the 

 study of the ultimate nature of protoplasm. 

 Thus, according to Biitschli, he ranks as 

 the first to demonstrate satisfactorily the 

 reticulo-vesicular character of protoplasm 

 in living tissue. His observations in 1870 

 in the follicle cells of Ascidia showed dis- 

 tinctly the reticular meshwork and the 

 breaking up of the cytoplasm into ultimate 



'vesicles.' He also indicated for the first 

 time (1870) the radial arrangement of the 

 alveoli around the nucleus, together with 

 the ' marginal alveolar layer. ' The term 

 ' paraplasm ' used by von Kupffer in 1875, 

 is still in use (as the equivalent of what at 

 present is more often known as 'metaplasm') 

 although in a somewhat different sense than 

 that in which it was first used. His sus- 

 tained interest in this theme was lately 

 shown in his inaugural address (1896) as 

 rector of the University of Munich, 



The processes of the fertilization of the 

 egg have been described by him in sev- 

 eral forms. In an early paper on this sub- 

 ject he expressed his belief that in large 

 meroblastic eggs a process of physiological 

 polyspermy occurs, a view which his stu- 

 dent. Professor Biickert, and other investi- 

 gators have since confirmed and extended. 

 His studies on fertilization have thus been 

 important as leading the way for other 

 papers from his laboratory — such for ex- 

 ample as those on the fertilization of the 

 lamprey and of the teleost by his devoted 

 friend, Dr. A. A. Bohm, and also the earlier 

 work of Theodor Boveri. 



Von Kupffer's work should next be noted 

 in connection with the structure of glands. 

 In his studies on the histology of the liver 

 he proved the presence of the secreting 

 vacuoles in the gland cells and of the in- 

 tralobular fibrous sheath. He next dis- 

 covered the remarkable Sfcernzellen (or 

 ' Kupffer's cells ') in the wall of the portal 

 capillaries : these he showed were not ner- 

 vous, as was at first believed, but highly 

 modified endothelial cells, and later he 

 demonstrated their function as phagocytes. 

 His researches on the development of the 

 mammalian kidney should here be men- 

 tioned : these he carried on by means of 

 serial sections cut by free hand — this was 

 long before the time when section cutting 

 became general — and by this means he was 

 able to demonstrate more satisfactorily than 



