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- 
tunitics for a man with scientific tastes, he entered upon that 
course of study in Tiibingen 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 
Tiibingen 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 Mohl’s studies on “plant schleim” 
there was a general movement toward the conclusion that 
the sarcode of the zodlogists 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- 
