C. DOBELL 



203 



Frequently no parasites could be demonstrated microscopically in the 

 snake's blood, although subsequent inoculation experiments proved 

 them to be present. The small forms were apparently formed by 

 the divisions of the original larger forms, and themselves underwent 



1. 



3. 



Fig. B. (1) Normal T. brucei in blood of rat. (2) T. hrucei in blood of grass snake- 

 eight days after inocalation. (3) T. brucei, giant form produced by inoculation from 

 grass snake back into rat. (4) T. lewiti, normal form during chronic infection in 

 blood of rat. (5) T. leicisi, form produced by passing the strain from rat through 

 grass snake, then frog, and then back into rat. Fourth rat passage, five days after 

 inoculation. [From Wendelstadt and Fellmer (1910), slightly diagrammatized.] 



The organisms are all drawn to the same scale, so that the differences in size are correctly 

 shown. 



division. They showed a slight change in their staining capacity. 

 When these small forms in the snake were inoculated back into rats, 

 they became very large, thus giving rise to a race of giant Trypano- 

 somes (Fig. B, 3). The increased size persisted for many divisions, 

 during passage through several rats\ In later passages, however, 

 the Trypanosomes diminished in size, and returned to their normal 

 dimensions. 



Closely similar results were obtained by passing the Trypanosomes 

 through tortoises ("europaische Sumpfschildkrote") and lizards ("graue 

 und Smaragdeidechsen ") : but no difference in size was observed after 

 passage through the salamander ("EIrdmolche"). A temporary increase 



^ When Trypanosomes (or other micro-organisms) are passed into a fresh host, or 

 culture medium, the new race which thus arises is frequently termed a new "generation " — 

 a vicious usage of the word borrowed from bacteriology. 



