112 THE ANIMAL PARASITES OF MAN 



ctenocephali is known to occur in the gut of Ctenocephalus canis 

 A natural Herpetomonas is also known in the gut of Pulex irritans, 

 as well as a Crithidia (C. pulicis, Porter). These natural flagellates of 

 the fleas pass through non-flagellate stages, like the Leishman-Donovan 

 body. In consequence Wenyon and Patton, among others, have 

 criticized Basile's results. Further, other investigators, such as 

 Wenyon and Da Silva (1913), have repeated Basile's flea experiments 

 and been unable to confirm them. 



In feeding and inoculation experiments the incubation period of 

 the parasite may be long, and so it is necessary to wait a long time to 

 see whether the parasite will develop. 



Immunity. Nicolle has tried some experiments with L. infantum 

 and L. tropica. He finds that in animals recovery from an attack of the 

 former confers immunity against infection by the latter and vice-versa. 



Laveran 1 records that a monkey having an immunity against L. 

 infantum was also immune to L. donovani. 



As mentioned on p. 103, Laveran and Franchini (1913), working in 

 Paris, have succeeded in inoculating Herpetomonas ctenocephali, a 

 natural flagellate in the gut of the flea, Ctenocephalus canis, into 

 white mice. Leishmaniform stages of the flea flagellate were re- 

 covered from the peritoneal exudate, blood and organs of the mice 

 some weeks after inoculation. The parasites may also be conveyed by 

 way of the digestive tract of the vertebrate. Similar experiments have 

 succeeded \vith H. pattoni. These experiments go to show, together 

 with those of Fantham and Porter with H.jacnlnm (seep. 104), that, in 

 the words of the latter authors, " it may be expected that the various 

 leishmaniases, occurring in different parts of the world, will prove to 

 be insect-borne herpetomoniases." 



Genus. Histoplasma, Darling, 1906. 



Under the name Histoplasma capsnlatum, 2 Darling described small 

 round or oval parasites, enclosed in a refractile capsule, and each con- 

 taining a single nucleus. The bodies were found in cases of spleno- 

 megaly in Panama. They occurred in the endothelial cells of the 

 small blood-vessels of the liver, spleen, lungs, intestine and lymphatic 

 glands, and also within the leucocytes. A few flagellates were stated to 

 occur in the lungs. The parasite has usually been placed near Leish- 

 inania, but recently Rocha-Lima has stated that Histoplasma is a yeast. 



Genus. Toxoplasma, Nicolle and Manceaux, 1908. 



The genus was created for crescentic, oval or reniform parasites, 2*5 p to 6 p. by 

 2 n to 3 ^, possessing a single nucleus and multiplying by binary fission. They occur 



1 Annales Inst. Pasteur (1914-15), xxviii, pp. 823, 885 ; xxix, pp. i, 71. 



2 fourn. Amer. Med. Assoc., xlvi, p. 1283 : fourn. ExptL Med. (1909), xi, p. 515. 



