178 



H. M. WOODCOCK, 



organs Avhicli react most strongly to the parasites^ and their 

 enlarged condition is probably to a great extent due to 

 enhanced activity in elaborating blood-corpuscles, leucocytes, 

 etc., to cope with the enemy. Laveran and Mesnil (40) 

 frequently noticed, in the peritoneal exudations of rats arti- 

 ficially infected with T. lewisi, instances of phagocytic 

 action by leucocytes upon the parasites (Fig. 6). Bradford 



Fig. 6. — Phagocytosis of T. lewisi. In A the leucocyte is com- 

 mencing to engulf the Trypanosome ; in B the latter is completely 

 intracellular ; c — E show the gradual dissolution of the parasite, 

 the two nuclear elements remaining longest recognisable, j) = 

 parasite ; n = nucleus of leucocyte ; c = ingested blood-corpuscles ; 

 V = vacuoles remaining after their dissolution. (After Laveran 

 and Mesnil.) 



and Plimmer (6) describe the same taking place in the spleen 

 of rats and mice infected with T. brucii, and also in the 

 blood of '' spleenless " animals (i. e. those from which this 

 organ has been extirpated). These authors conclude that, 

 at any rate in the earlier stages of the disease, a good deal of 

 phagocytic action takes place in the spleen. Castellani (15), 

 again, has observed phagocytosis of T. gambiense. 



But it is probable, also, that the hasmatopoetic organs or 

 lymphatic glands secrete some chemical or physiological 

 substance which exerts a harmful action upon the Trypano- 

 somes and causes them to undergo involution, assuming 



