238 THE PATHOGENIC FLAGELLATES 



other hand, there is no evidence, according to Fatten, of parasites 

 in the body cavity, nor in the nymphs and larvee reared from the 

 egg. In this form, therefore, inheritance appears to be out of the 

 question, the insects becoming infected solely by the ingestion of 

 encysted forms of the parasite. 



As in trypanosoma, the various species of herpetomonas are char- 

 acterized by the habit of forming rosettes or agglomerations through 

 the union of individuals by the flagellated ends. Also, in common 

 with trypanosomes and with the merozoites of malaria organisms, they 

 manifest a well-marked rheotropism or reaction against a current, a 

 property, especially in the latter case, which enables the organism to 

 make headway against a blood flow or intestinal current. 



In all forms of herpetomonas there are free-moving monadiform 

 parasites, or motile gregariform parasites, which move with a worm- 

 like motion and finally aggregate about the epithelial cells, where they 

 often form masses of considerable size. In both of these conditions 

 the organisms may reproduce by longitudinal division. The gregari- 

 form phase may also encyst by secreting a slimy covering, which 

 becomes more or less hardened, and in this cyst the organisms pass out 

 of the digestive tract with the feces, thus serving to spread the infection. 



The history of Herpetojnonas donovani, Lav. and Mes., is par- 

 ticularly interesting from both the medical and the biological points 

 of view, and shows the devious paths which an organism may follow 

 before reaching its definitive place in a zo5logical system. The etiology 

 of a number of peculiar diseases of India, characterized by well- 

 marked splenomegaly (dum dum fever, kala azar "black sickness"), 

 by irregularly recurrent fevers, anemia, and emaciation, resulting 

 finally in profound cachexia and usually in death, has been only 

 recently established. Leishman ('0.3) found peculiar bodies in cells 

 obtained in films from a postmortem, and considered them degenerated 

 forms of trypanosomes ; from this they were given the name of " Leish- 

 man bodies." Donovan ('03) found peculiar bodies in the peripheral 

 blood of cases of kala azar, and sent his preparations to Laveran and 

 Mesnil, who, in November, 1903, described the peculiar bodies as 

 similar to the blood parasites of Texas fever (babesia "piroplasma") 

 and named the organism accordingly Piroplasma doiwvaiii. From 

 this the bodies became known as the " Leishman-Donovan bodies," 

 although considerable difference of opinion existed as to the identity 

 of the forms in the spleen and in the blood. In December, 1903, 

 Wright described peculiar structures, which he interpreted as organ- 

 isms belonging to the microsporidia, in a case of tropical ulcer, and 

 named the organism Ilelcosoma tropicum. Having a well-marked 

 resemblance to the bodies found in kala azar, these new structures 

 added a third term to the series, and they became known as the 

 "Leishman-Donovan-Wright bodies" (Woodcock). In the meantime, 



