372 



TR VP A NO SO MI DM 



Instead of proceeding directly to flagellation, the parasite may show a 

 division of its nuclei into two, with the formation of two flagella, and then 

 division into two flagellate parasites, or the nuclei may multiply without 

 division of the cytoplasm, so that forms containing four to eight nuclei may 

 be found together, which eventually break up into separate flagellate forms. 

 Patton has traced the development into the post-fiagellate stage, and 

 believes that if the bug is fed upon human or monkey's blood the flagellates 

 are quickly destroyed, but if not so fed the cycle of development is completed 

 in ten to twelve days after a single feed. He believes that this destruction of 

 the flagellates by warm blood is the cause of the endemicity of the disease. 



Donovan suggests that th^ true host may be Conorhinus rubro- 

 fasciatus, but Patton finds that the parasite in this bug degenerates 

 and never flagellates. 



Further, the evidence so far collected does not support the possi- 

 bility of the bug, the flea, the mosquito, the phlebotomus, the 

 domestic fly, the louse, or the tick as being the causal agent. It will 

 be remembered that all these arthropods possess flagellates of their 

 own, which the researches of Fantham and Porter, and Laveran 

 and Franchini, have shown to be capable of producing disease and 

 death in mammals when injected {vide p. 363). 



As examples of flagellates occurring in bugs we may quote: — 

 Herpetomonas lygcei in Lygceus militaris, found in the Sudan and 

 investigated by Archibald ; H. hospei in LygcBUs hospes ; H. aspongopi 

 Aders in Aspongopus viduatus (Sudan); H . pyrrhocori in Pyrrhocoris 

 aptera ; also Crithidia in Cletus varius, Gerris fossorum, Conorhinus 

 rubrofasciatus, Leptocoris trivittatus ; also a trypanosome in Neotoma 

 fuscipes. It is therefore possible that the last word has not yet 

 been said with regard to arthropods and their flagellates as the 

 causal agent of kala-azar. 



Archibald's experiments with the Sudan variety are very sugges- 

 tive that the infection may be per os. The cycle may possibly be 

 from man via the fseces to some water arthropod, from which it may 

 escape also via the fseces into water, and so via the mouth into 

 the alimentary tract and system of man, but this is not yet proved. 

 With reference to this it should be remembered that Fantham and 

 Porter infected young rats by feeding with Nepea cinerea containing 

 Herpetomonas jaculum. 



The present state of our knowledge with regard to this parasite is that it is 

 the cause of the disease called kala-azar ; and that it is probably spread by 

 means of some arthropod, but the particular carrier is not known. 



Geographical. — The parasite is known to occur in India, Ceylon, China, 

 Arabia, Egypt, and the Sudan, and many parts of Africa. 



Morphology. — The parasite is round, oval, or pyriform in shape, measuring 

 2 to 3'5 fA, in length by i '5 to 2 in breadth, with a granular cytoplasm con- 

 taining two chromatic masses: the larger, more rounded, stains shghtly; the 

 smaller, rod-shaped, stains deeply. From the latter a linear structure (Mesnil 

 and Novy's rhizoplast) runs to the acute end. A vacuole is also often present. 



Distribution in the Body. — The parasites are found sometimes in large 

 numbers in endothelial cells in the capillaries of the liver, spleen, bone-marrow, 

 lymphatic glands, and mucosa of the intestine, in the blood from the femoral, 

 portal, and hepatic veins, and more rarely in the circulating blood shortly 

 before death. 



Parasites liberated from the large cells are apparently taken up by mono- 



