474 GROWTH OF BIOLOGY IN THE NINETEENTH CENTURY. 



late mechanism, and believed in the explanation of life as a purely 

 chemo-ph3'sical process. 



The iirst consequence was that physiologists in the regular line of 

 the profession, with few exceptions, cultivated, l)v preference, only 

 such fields as were adapted to chemo-physical methods of research, 

 and left others, such as the physiology of development and gener- 

 ation, altogether untilled. But anatomists, zoologists, and botanists 

 only insisted upon them so much the more. They penetrated deeper 

 into the vital phenomena of the cell, of ])rotoi)lasni. and of the 

 nucleus. They discovered the wonderfully^ complicated process of 

 the division of the mideus, the spindle with its ray figures, and 

 the centrosomes, the chrt)mosomes, and their longitudinal segmen- 

 tation, and finally they solved the old controversy which had once 

 divided physiologists into the two camps of the animalculists and the 

 ovists, for now the secret process of f«'rtilization was hap})ily settled 

 in all its phases by simple microscopical observation. The penetration 

 of a spermatozoon into an ogg cell, the coalescence of the egg nucleus 

 and the sperm luicleus were successfully and directly observed. They 

 deepened the comprehension of the entire process by the discovery 

 that egg and sperm cells nuist l)e prepared, in some sort, for the fruc- 

 tification, by the reduction or expulsion of half the matter of their 

 nucleus, and finally, supported by these and other facts, they ventured 

 to lay the foundation for the problem of heredity by the hypothesis 

 that in the matter of the nucleus the vehicles of inherited characters 

 are found. ♦ 



So l)y the side of the chemo-physical school of j^hysiology an anatomo- 

 biological bias gained strength. This endeavored to deepen our inspec- 

 tion of life by microscopical research. But the anatomo-biological 

 bias, the more it enforces itself (sich geltung verschafft) by its investi- 

 gation of the organization of the substratum of life, will the more lead 

 to the insight that the mechanical standpoint in biology is just as one- 

 sided as the vitalistic. Truly one of the chief champions of the mech- 

 anistic doctrine — Du Bois-Reymond — has himself applied the critical 

 probe to it and, in principle, has recognized its insufficiency. In his 

 address upon the limits of the knowledge of nature he has set up two 

 insoluble interrogation marks, which later, in his seven world riddles, 

 he has increased to seven, and, really, 1 do not know why he should 

 have restricted himself to so modest a number. Du Bois-Reymond 

 characterizes the impossibility on the one hand of conceiving the 

 essence of matter and force, and on the other hand of explaining even 

 the lowest degree of consciousness mechanically, as a trite truth, and 

 saA'S that it is an old experience, which no discover}^ of natural science 

 has in the least modified, that one equally fails whether one adopts the 

 theory of atomism, of dj^namism, or the opinion of plenum. 



Du Bois-Re^^mond, it is true, has not himself drawn the conclusion 

 which necessaril}' follows from this. But the conclusion which in the 



