102 Messrs. Kanthack, Durham, and Blandford. 



We found, however, that guinea-pigs are susceptible to riagana under 

 ordinary conditions, but that, as a rule, the disease in them is more 

 protracted than in rabbits, rats, mice, cats or dogs, and even horses ; so 

 that they are distinctly more resistant than these animals. In no 

 instance, however, has recovery ensued after haamatozoa have once 

 appeared in the blood. 



According to unpublished observations by Bruce upon the Tsetse 

 Fly Disease in South Africa, it appears that native goats and sheep are 

 to some extent refractory, the disease, as a rule, running a chronic 

 course (five months). 



A monkey (Maeacm rhrxu-s) was also tried. It died in about two 

 weeks in an advanced condition of pulmonary tuberculosis, but the 

 presence of abundant hsematozoa had been determined in the blood 

 during life up to the time of death. 



A weasel was injected. It showed hsematozoa in its blood, and died 

 a few days later, but death almost certainly. was hastened by the effects 

 of captivity. 



Pigeons are the only birds which have yet been tried. The pigeons 

 after inoculation did not show signs of the disease, nor was their blood 

 infective. It may be mentioned that Bruce tried South African hens 

 without success. Further experiments with birds are in hand. 



Young animals, if susceptible (kittens and puppies), as a rule have 

 died earlier than adults, and while suckling they are still more highly 

 predisposed ; young guinea-pigs, however, are comparable to older ones 

 in their resistance. 



The fcetus in utero of infected rabbits, guinea-pigs or rats, is not 

 infected, although the mother's blood may contain a large number of 

 hsematozoa. The latter are to be found in the placenta, but not in the 

 foetal blood. Similar observations have also been made by Lewis,* 

 Lingard,t and EougetJ in their investigations on allied hsematozoa. 



II. Duration of Disease in the different Animals. 



As will be seen from the figures given below, the lethal period varies 

 somewhat in each species of susceptible animal. The duration of the 

 disease appears to depend principally upon the individual suscepti- 

 bility rather than on the mode of inoculation or the quantity of 

 infective material introduced. Thus, of four rabbits inoculated in the 

 same manner with the same material, three died on the 12th, 2 1st,- and 

 24th days respectively, whilst the fourth was killed on the 41st day ; 

 many similar instances could be cited. Nor does a larger quantity 

 necessarily determine a more rapid death ; thus a rabbit which has 



* ' Physiol. and Patliol. Eesearches,' p. 630. 



t ' Summary of Further Eeport on Surra,' 1895. 



J ' Annales de 1'Institut Pasteur/ 1896, p. 716. 



