414 FAMILY: TRYPANOSOMID^E 



produce infection so readily. Animals may be infected by injection of 

 large doses of the cultural forms, but infection is less likely to take place 

 than after a dose of the virus from the organs of man or another animal. 

 Organisms which have been maintained by subculture for long periods 

 are less liable to infect than those more recently isolated. 



The infected animals often recover, and, as has been clearly demon- 

 strated by Laveran, on the passage of the virus from animal to animal it 

 loses its virulence to such an extent that finally infection does not occur. 

 This is equally true of the mouse, dog, and monkey — the animals which 

 have been used to the largest extent — though from the recent observations 

 of Young, Smyly, and Brown (1924) in North China, the hamster appears 

 to be more susceptible. The majority of animals, if young when inoculated, 

 continue to increase in weight in spite of their infection, though subject 

 to minor disturbances of health such as slight attacks of fever. In some 

 cases the infection is more acute, and after a rapid loss of weight death 

 occurs. 



The infection produced in experimental animals is of slow develop- 

 ment, and cannot be compared with that resulting from the inoculation 

 of pathogenic trypanosomes. The lack of a suitable experimental animal 

 has been a great handicap to investigation work. 



In some cases, by the inoculation of the skin, observers have been able 

 to produce with L. donovani local cutaneous lesions resembling oriental 

 sore. 



Shortt (19236) inoculated a number of caterpillars and other inverte- 

 brates with cultures of L. donovani. In the case of one caterpillar, active 

 single and dividing flagellates were found in the body cavity fluid a week 

 later. 



The Mediterranean virus has been successfully inoculated into dogs by several 

 observers since Nicolle's first success in 1908. Jemma, di Cristina, and Cannata 

 (1910) were successful in Italy, and Novy (1908) in America with a culture which 

 had been sent to him. NicoUe and Blaizot (1912) proved that the jackal was also 

 susceptible. Yakimoff (1915rt), working in Turkestan, succeeded in infecting dogs 

 and mice with the local virus. The most extensive series of experiments with dogs 

 has been made by Laveran (1917), who employed a virus obtained in Tunis. Of 

 thirty dogs inoculated with material from the organs of infected animals, twenty-six 

 became infected. In five dogs which died of the disease, the average duration was 

 257 days. Two dogs killed on the 454th and 456th days were still found infected, 

 though the condition of the organs showed them to be on the road to recovery. 

 Nicolle and Laveran have both noted keratitis in infected dogs. The Indian virus 

 was first inoculated to dogs by Donovan (1913). At about the same time Patton 

 (1913) was also successful with the dog and jackal. The writer (1914rt, 1915a) in 

 London infected a dog from a case of kala azar from India. Subsequently the virus 

 was passed through four successive dogs, when the inoculations were discontinued. 

 Mackie (19156) also succeeded in infecting dogs with the Indian virus. Laveran 

 (1913, 1917), commencing with a culture of L. donovani obtained from Row in India, 



