Posterior lenticonus with involvement of foetal nucleus

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Resistance to extinction as a function of differential levels of drive and effortfulness of response

Rats were trained on a crf schedule for bar-pressing requiring different amounts of force to activate the food delivery mechanism. Ss were given 480 reinforced trials under either low, medium, or high food deprivation. Extinction data showed a significant effect of food deprivation; however, neither effortfulness of responses nor its interaction with deprivation was significant.

The Culex pipiens fatigans problem in South-East Asia with special reference to urbanization

In South-East Asia in recent years urbanization has proceeded rapidly. Because of limited financial resources it has seldom been possible to provide sufficient sanitation; this has led to conditions favourable to the breeding of Culex pipiens fatigans. The density of C. p. fatigans is higher in urban areas than in rural ones. Differences in infection and infectivity rates in C. p. fatigans seem to be due to differences in infection rates in the human population rather than to differences in the life-span of the mosquito. Precipitin tests have shown that the species feeds predominantly on man. It breeds in almost any type of stagnant water with organic contamination. Filariasis problems in India have been classified according to the duration of established transmission.