The mechanisms which affect the periodic cycle of Pacific Wuchereria bancrofti microfilariae.

1. Investigations were made of the effect of various procedures in raising or lowering the microfilaria count of Pacific type Wuchereria bancrofti in the peripheral blood. 2.

The resistance of Trypanosoma congolense, T. vivax and T. evansi to human plasma.

Tests were made in mice on the resistance of cattle trypanosomes to human plasma. 12 stocks of Trypanosoma, congolense were tested' three were fully resistant, eight were moderately or highly resistant, and one was fully sensitive. Four stocks of T.

The resistance to human plasma of Trypanosoma brucei, T. rhodesiense and T. gambiense. II. Survey of strains from East Africa and Nigeria.

Tests were made in vivo of the sensitivity or resistance to human plasma of many strains of polymorphic trypanosomes. Five strains of T. gambiense from Nigeria were tested and all were highly resistant.

The resistance to human plasma of Trypanosoma brucei, T. rhodesiense and T. gambiense. I. Analysis of the composition of trypanosome strains.

The sensitivity of strains of polymorphic trypanosomes to human plasma was investigated in mice. By measuring the prepatent period an approximate estimate could be made of how many trypanosomes resisted each of a graded series of doses of plasma and survived to produce infection. In this way the composition of typical strains could be analysed.

The resistance to human plasma of Trypanosoma brucei, T. rhodesiense and T. gambiense: III. Clones of two plasma-resistant strains.

Tests for resistance to human plasma were made on six clones of a stabilate of Trypanosoma rhodesiense (LUMP 10) which was calculated to contain about 3,000 resistant trypanosomes per million. Two of the clones were not resistant and four were only subresistant. Tests were also made on 12 lines (clones) of a stabilate of polymorphic trypanosomes isolated from tsetse flies.