116 Messrs. Kanthack, Durham, and Blandford. ' 



while others lived for 17 23 days. As a curative agent this serum 

 was useless ; guinea-pigs serum also had no preventive action. 



X. Biology of the Nagana Hcematozoon. 



So far our knowledge of the nagana parasite, as that of other Try- 

 panosomas, is very incomplete. Kouget* has failed to find forms corre- 

 sponding to those described by Danilevsky in birds and by Shala- 

 shnikov in rats, and Lewis and others have been equally unsuccessful, 

 while it is difficult to follow Lingard in his description of young forms. 

 We have not succeeded in tracing a life history, and we are still in 

 search of developmental forms, a task which at present occupies our 

 special attention. 



1. Most commonly in blood, &c., drawn from infected animals the 

 forms described by Bruce are found. They are generally in active 

 movement, and can sometimes be observed in* locomotion with their 

 liagellated end forwards, as Lewis described in the case of other hsema- 

 tozoa ; in many cases they do not change their position by free swim- 

 ming, but tend to fix themselves by one or other end to the coverslip 

 or to corpuscles or cells in the specimen ; they then exhibit more or less 

 rapid oscillations, and may change their position by apparently draw- 

 ing or pushing themselves in one direction or the other. Meanwhile 

 the vibratile membrane waves rapidly and the protoplasmic body alters 

 in shape, becoming thicker and shorter or thinner and longer ; in the 

 case of the English rat haematozoon free swimming is the rule ; changes 

 in the shape of the body like those of the nagana organism are not 

 observed. 



2. The nagana parasites vary considerably both in size and form ; 

 they may be long and pointed or blunt-ended and somewhat stouter ; 

 some individuals are short and thick with a short flagellum, their proto- 

 plasm being crowded with rounded granules. Still larger forms possess- 

 ing more than one vibratile membrane are sometimes, though rarely, 

 met with. 



3. Especially in specimens taken from lymphatic glands, but also in 

 specimens obtained from the blood, &c., there is a clear vacuole at the 

 thick end ; this does not become stained with staining reagents ; it 

 varies much in size in the different individuals, but we have watched in 

 vain for evidence that it is of a contractile nature. 



4. By means of haemalum or hsematoxylin a nuclear body can be 

 demonstrated in the middle of the parasite ; it is usually oval, but may 

 be more saddle-shaped. The protoplasm also contains a number of 

 granules which stain with basophil reaction (methylene-blue, thionin, 

 &c.) } these are somewhat variable in number, being fewer in specimens 

 in which the protoplasm is more refractive, e.g., from lymphatic gland. 



* Loo. cit., pp. 722 and 723. 



