270 BIOLOGY AND ITS MAKERS 



protoplasm, stands somewhat aside, but his name, neverthe- 

 less, should be connected with the establishment of the 

 protoplasm doctrine. 



Von Mohl (Fig. 85) was an important man in botany. 

 Early in life he showed a great love for natural science, and 

 as in his day medical instruction afforded the best oppor- 

 tunities for a man with scientific tastes, he entered upon that 

 course of study in Tubingen at the age of eighteen. He took 

 his degree of doctor of medicine in 1823, and spent several 

 years in Munich. He became professor of physiology in 

 Bern in 1832, and three years later was transferred to 

 Tubingen as professor of botany. Here he remained to the 

 end of his life, refusing invitations to institutions elsewhere. 

 He never married, and, without the cares and joys of a 

 family, led a solitary and uneventful life, devoted to botan- 

 ical investigation. 



Cohn. After Von MohPs studies on "plant schlcim ' 

 there was a general movement toward the conclusion that 

 the sarcode of the zoologists and the protoplasm of the bot- 

 anists were one and the same substance. This notion was in 

 the minds of more than one worker, but it is perhaps to Fer- 

 dinand Cohn (1828-1898) that the credit should be given 

 for bringing the question to a head. After a study of the 

 remarkable movements of the active spores of one of the 

 simplest plants (protococcus), he said that vegetable proto- 

 plasm and animal sarcode, "if not identical, must be, at 

 any rate, in the highest degree analogous substances ' 

 (Geddes). 



Cohn (Fig. 86) was for nearly forty years professor of 

 botany in the University of Breslau, and during his long life 

 as an investigator greatly advanced the knowledge of bac- 

 teria. His statement referred to above was made when he 

 was twenty-two years of age, and ran too far ahead of the 

 evidence then accumulated; it merely anticipated the com- 



