394 SPECIFIC MICRO-ORGANISMS 



flagella and resemble the intracellular forms of Leishmania. From 

 these cysts the parasites escape into the blood, where they are 

 found as trypanosomes in the blood plasma. Slender and thick 

 forms occur here, the difference probably depending upon the 

 age of the parasites. 



Monkeys, rats, mice, young guinea-pigs and many other 

 mammals are susceptible to inoculation. The infection is trans- 

 mitted by a bug, Conorhinus megistus, 

 in which the protozoon develops 

 abundantly. The bedbug, Culex 



lectularius also is capable of trans- kj? C\ *~" 



mitting the disease. f*r\ *\^' 



Cultures are readily obtained %4^ ' 

 on blood-agar and Chagas was p IG> , 6 1 .-Schizotrypanum 

 able to infect animals with such cul- cruzi in human blood. (From 



Doflein after Chagas.) 



tures. 



Leishmania Donovani. Laveran and Mesnil in 1903 described 

 this protozoon which occurs inside cells in various parts of the 

 body, but is especially abundant in the spleen and liver, in the dis- 

 ease known in India as Kala-Azar or tropical splenomegaly. The 

 organism is oval, 2 to 4/4 in diameter, finely granular and some- 

 times vacuolated. In the interior there is a large rounded nucleus 

 and a smaller oval or rod-shaped blepharoplast, near which a third 

 very slender short thread may usually be recognized as the rudi- 

 ment of the undeveloped flagellum. These structures are doubled 

 in the division stages. Multiple division also occurs. In the cir- 

 culating blood the organism is found within lymphocytes and poly- 

 nuclear leukocytes. Many of them may be found in a single cell. 



Cultures are readily obtained by inoculating fluid (citrated) 

 blood with blood or with spleen juice containing the parasites, or 

 by inoculating the usual blood-agar. In artificial culture the 

 cell elongates, the rudimentary whip extends into a true flagellum 

 and the organism assumes the appearance of a typical leptomonas 

 (herpetomonas). Little difficulty is experienced in keeping the 

 cultures alive and flourishing. 



