42 Society for Experimental Biology and Medicine. 



comes into play in any specific case depends upon the nature 

 of the material which is swallowed. We said that liquid is squirted 

 down, but I am quite sure that thick syrup is not squirted farther 

 than the upper part of the esophagus, if so far. We said that 

 semi-liquids or semi-solids are also thrown down. We came to 

 this conclusion from observations made on the swallowing of bread 

 thoroughly softened in water. Possibly in this case a separation 

 took place and the water was thrown down while the bread or 

 some of it stuck to the wall of the gullet and was later gathered 

 up by the peristalsis. It is not improbable that this is what occurs 

 when a mixture of bismuth and water is swallowed. The water 

 may be squirted down, while a large part of the bismuth may stick 

 to the wall and be gathered up later by the succeeding peristalsis — 

 and it is the latter which is probably seen through the fluoroscope. 



32 (175) 



Immunity against trypanosomes. 



By F. G. NOVY. 



[From the Hygienic Laboratory of the University of Michigan.^ 

 It is an establised fact that rats which have recovered from an in- 

 fection with Tr. Lewisi are immune to subsequent inoculation with 

 that species of flagellate. The same holds true for cattle, sheep, 

 goats, etc., that have recovered from the infection caused by the 

 pathogenic trypanosomes, such as nagana, surra and dourine. 

 This condition of active immunity is seemingly possible only in 

 those species of animals that are relatively insusceptible, for with 

 really susceptible species the infection is always fatal. 



Heretofore all experiments on artificial immunity against try- 

 panosomes have been made on animals that have recovered from 

 the effects of the parasite which has been living and multiplying 

 in the blood-vessels of that animal. Now that cultures of some of 

 these organisms, as for example Tr. Leivisi of the rat and Tr. 

 brucei of nagana, are possible it was desirable to ascertain whether 

 or not they could be used to immunize against the virulent organ- 

 isms. It may be said, in passing, that cultures of both of these 

 trypanosomes, even after they have passed through a hundred 

 generations or subcultures in the course of two years, do not be- 



