TO Aug., J91. 



The Etiology of Contagious Diseases. 



493 



a tube will remain sterile for an indefinite period, providing unfiltered 

 air does not gain access to the tute (Fig. 7). The method 

 of cultivating is to take a small quantity of the material under 



FIG. 



10. HIPPOBOSEA 

 RUFIPES. 



A transmitter of Trypauo- 

 somes. 



FIG. 



1 I . PARASITE.S IN HIND GUT 

 OF FLEA. 



consideration on the point of a fine needle (figure) previously 

 heated to destroy life on it. This is introduced carefullv into 

 the test tube and the surface of the gelatine slightly touched (figure). 

 The tube is then plugged with cotton wool to prevent impure air entering. 



FIG. 12. PIROPLASM IN RED BLOOD CELLS. 



and warmth is supplied by means of an incubator (Fig. 8), and within a 

 few hours a crop will appear on and around the side that has been touched 

 b\ the needle. The growths that result — or. as they- are termed. " cuU 

 tures " — have, in many cases, characteristic appearances, which assist 



