436 W. HANNA. 



Laveran and Mesuil have shown that the disease can be 

 conveyed from rat to rat by the agency of fleas. 



Surra, a disease affecting horses and mules in India and 

 Burraah, has been shown by Evans to be due to a trypano- 

 soma (T. Evan si [7]). 



Lt.-Col. Bruce, in 1896, described the occurrence of nagana 

 amongst horses and cattle in Central Africa, and probably in 

 other parts, and discovered the cause to be a try panose nia 

 (T. Brucei [8]) in the blood of the animals. 



In South America a disease, mal de caderas, very similar to 

 surra and nagana, has been described. In this case also a 

 similar pai-asite has been discovered as the causative agent, 

 which Laveran and Mesnil state to be identical with that of 

 nagana. 



Comparing T. Lewi si of the rat with T. Brucei of nagana, 

 the former is much thinner; it is not so long as T. Brucei, 

 which varies from 26 to 28 fx. The posterior end of T. L e w i s i 

 is pointed; that of T. Brucei is blunt. T. Brucei has a 

 large centrally placed macronucleus, and the body has many 

 curves. 



From the work of Koch (9) in connection with the para- 

 sites, and of Rodgers (10) on the symptoms of surra and 

 nagana, it is not improbable that these two diseases are 

 identical, though this has not been proved. 



Bloodsucking flies, such as horse-flies (Tabanus) and the 

 tsetse fly (Glossina), are the transmitting agents in these 

 diseases. 



In dourine (H), a disease affecting horses, the trypanosoma 

 parasites (T. equip erdum) are rare in the blood, but occur 

 mostly in the sero-sanguineous fluid in the local oedemas, and 

 in the mucous membranes of the parts affected. 



In February, 1902, a large and distinct species of trypano- 

 soma pathogenic to cattle was discovered by Dr. Theilcr (12) 

 in the Transvaal. 



The most interesting development regarding these para- 

 sites, however, is the comparatively recent discovery of their 

 presence in the blood of man in Africa by various observers 



