43 



Serum of Immune Animals.— Professor Koch had stated that the 

 serum of cattle which were hyperimmunised with the blood of cattle 

 suffering from East Coast fever acted, when injected into sick oxen, 

 directly on the parasite, causing them to disappear ; unfortunately such 

 serum had also haemolytic effect, so that it could not be apphed with 

 safety. Having overcome the difficulty of haemolysis in horses by 

 infusion of the virulent blood into the jugular vein, this method was 

 also used in connection with East Coast fever and some oxen were 

 hyperimmunised to the extent of a minimum of 20 and a maximum of 40 

 litres. 



This serum was not haemolytic. It had no lytic action on the parasite, 

 and when applied on an infected herd it had no preventive action. 



Conclusion. — Serum of East Coast fever immune oxen hyperimmunised 

 by infusion of sick blood has no preventive action whatsoever. 



Resume. 



The immimity in East Coast fever is complete concerning natural 

 infection and time. 



The immune animals do not retain the infection in the blood. 

 The serum has no preventive properties. 



v.— TRYPANOSOMIASES. 



There exist many different species of these parasites in Africa, which 

 from our point of view have not yet been studied. A certain number of 

 records are registered in the literature, which will give us an idea as to 

 the existence of immunity or otherwise. I shall only refer to these 

 trypanosomiases. 



The specific trypanosomiasis of cattle in South Africa is due to the 

 presence of Trypanosoma theileri. Generally speaking, this parasite has 

 but little pathogenic action ; we meet it occasionally in bloodsmears 

 sent to us from cattle reported as suffering from gall-sickness, invariably 

 from the bushveld. This trypanosomiasis is only inoculable into cattle. 

 Recovery from such an attack seems to create immunity. 



The inoculation of large quantities of blood containing the 

 trypanosomes into animals which had recovered from trypanosome infec- 

 tion gave in the majority of cases negative results, and in the positive 

 results there were only a small number of parasites. 



Conclusion. — Immunity caused by the recovery from a Trypanosoma 

 theileri infection, can be broken by subsequent inoculation. 



Of more importance are the trypanosomes of Trypanosoma evansi, 

 the type to which belong, in addition to the one mentioned, Trypanosoma 

 brucei of Zululand,' of Togo in West Africa, and the Trypanosoma 



