SEVENTEENTH AND EIGHTEENTH CENTURIES X49 



for his doctor's degree, he published in 1759 the essay which was to make 

 his name famous. Having served for a time as an army surgeon, he applied 

 for and obtained permission to hold lectures in medicine in Berlin, which, 

 however, resulted in his coming into serious conflict with the professors 

 at the Collegium Medicum. Being of a peaceful disposition he was much 

 troubled at this and was delighted when he received a summons to St. Peters- 

 burg, where he became an academician and spent the rest of his life carrying 

 on his research work in peace. He died in 1794. 



Woljf's generation theory 

 Caspar Friedrich Wolff is one of those who did not win fame until after 

 death. His own age paid little attention to him. Haller, to whom he dedi- 

 cated his afterwards famous treatise Theoria generationis, accepted the honour 

 in a friendly spirit, but paid little attention to the work, as also did other 

 biologists of the period. That Wolff was thus misunderstood by his con- 

 temporaries was due mostly to the fact that from the very outset he adopted 

 a course directly opposed to the then prevailing conception of the phenomena 

 of life; he began with a ready-made theoretical program, and the facts he 

 presents are collected for the express purpose of proving his already firmly 

 established convictions. By way of introduction he lays down the plan of 

 his work; by the body's '' generatio," or, as we should now call it, "evolu- 

 tion," is meant its creation Q' fonnatio"^ in all its parts, and its principle 

 is the force that brings about this creation. The upholders of the doctrine 

 of "predelineation" thus deny, he adds, that any "generation" takes place 

 at all. He starts, therefore, by declaring war on the preformation theory; 

 he does not base his rejection of it on the evidence of the facts he has ob- 

 served, but on purely theoretical reasons adduced by Christian Wolff's philo- 

 sophical methods. "He gives a true explanation of generation who derives 

 the parts of the body and their composition from the fixed principles and 

 laws governing them; . . . and he has perfected a theory of generation 

 who has succeeded in tracing the entire ready-formed body from these prin- 

 ciples and laws." The principles on which the fresh formation of organism 

 takes place are food and growth; food re-creates the simple components of 

 the organism, while through growth are formed entire parts of the body or 

 fresh bodies. Reproduction is, in fact, brought about by a "weakened growth 

 (yegetatio languescens)," whereby the newly-formed seed or embryo is sepa- 

 rated from the mother plant or animal and is prevented from growing further 

 in union with the latter. And that which produces all nourishment and 

 growth is, according to Wolff, the "inner force (vis essentialis^," a term 

 which he constantly uses to mean the ultimate cause of all that takes place 



arise out of nothing, which is impossible. For the rest, he was a clever mathematician and, for 

 his age, a sound botanist, and contributed much towards inculcating an interest in natural 

 science in Germany. 



