SYNOPSIS. Haemogregarina echisi n. sp. from the saw‐scaled viper Echis carinatus of West Pakistan is described. Eleven of 40 vipers were infected. The blood forms were almost entirely intraerythrocytic and were enclosed in a capsule. There was obvious hypertrophy of the host cell, and multiple infection of a single host cell was common. Extracellular forms were also present; they were longer than intracellular forms. No sexual dimorphism was noticeable. Schizogonic stages, from early to mature, were found in abundance in the lung capillaries. The number of merozoites per schizont was normally 22–25, altho as many as 38 merozoites were present in some schizonts. The few mites that could be collected from these snakes were free from any developmental stage of the parasite. Dimorphic schizogony, described in some haemogregarines, was not found. The status of the genera Hepatozoon and Haemogregarina, and the specific differentiation is discussed.
SYNOPSIS. Development of Trypanosoma lewisi in chimaeric mice with and without rat serum supplements was studied in 5 protocols. Chimaeric mice were male and female C3H/An Cum and 1C3F1, [(101/CUM × C3H/An Cum) F1] exposed to 950‐1000 R of whole‐body X‐irradiation. Their hemopoietic systems were replaced with Sprague‐Dawley rat bone marrow.
Trypanosomes did not develop in any mice not supplemented with rat serum. Ih those chimaeric and normal mice given rat serum the trypanosomes grew and developed large populations, more so in chimaeric than in normal animals.
The development of this trypanosome cell in heterologous mice is viewed as mediated principally thru nutritional factors supplied by rat serum with alteration of host‐immune status being of lesser importance.
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