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 recovered 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 with _H. pattoni_. These experiments go to show, together with those of Fantham and Porter with _H. jaculum_ (see p. 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 capsulatum_,[139] Darling described small round or oval parasites, enclosed in a refractile capsule, and each containing a single nucleus. The bodies were found in cases of splenomegaly 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 _Leishmania_, but recently Rocha-Lima has stated that _Histoplasma_ is a yeast. [139] _Journ. Amer. Med. Assoc._, xlvi, p. 1283: _Journ. Exptl. Med._ (1909), xi, p. 515. Genus. *Toxoplasma*, Nicolle and Manceaux, 1908. The genus was created for crescentic, oval or reniform parasites, 2·5 µ to 6 µ by 2 µ to 3 µ, possessing a single nucleus and multiplying by binary fission. They occur in mononuclear and polymorphonuclear cells in the blood, spleen, liver, peritoneum etc. (fig. 51). The parasites have been found in the gondi, dog, rabbit, mole, mouse, pigeon and other birds. Although various species names have been given to the parasites in these hosts, it seems probable, from cross infection experiments, that there is but one species with several physiological races. Splendore[140] (1913) has described a flagellate stage. [140] _Bull. Soc. Path. Exot._, vi, p. 318. [Illustration: FIG. 51.--_Toxoplasma gondii_, endocellular or free in the peritoneal exudate of infected mice. 1, 2, mononuclear leucocytes containing toxoplasms. 3, polynuclear, containing parasites. 4, 5, 6, endothelial cells containing toxoplasms, agglomerated in 6. 7, agglomeration forms. 8–11, free forms. 12–13, division stages. × 1,600. (After Laveran and Marullaz.)] [Illustration: FIG. 52.--_Toxoplasma pyrogenes._ 1, body found in blood. 2–7, bodies found] in spleen. [1 is about the size of a red blood corpuscle, as drawn in the figures]. Magnification not stated. (After Castellani.)]