Vascular patterns of the mammalian testis and their functional significance.

Even a superficial examination of the testes of various animals, for example rat and rabbit, is sufficient to make obvious that there are fundamental differences in their vascular supply and that the vessels display remarkable complexity both in their venous and arterial course. That morphological differences may exist between different animals has long been realized; thus de Graff (1677) clearly depicts the contrasting patterns of dog and dormouse. Nevertheless, comparative studies of these patterns have been meagre and their functional significance has not been elucidated. In this communication is presented first a description of these testicular vascular patterns in a number of animals, drawing attention especially to the course and relations of the vessels within the spermatic cord. In a second section evidence is offered in support of the suggestion that the morphology of the blood vessels in the cord is connected with the temperature regulating mechanism of the testis—specifically, as a determining factor of the abdomino-testicular temperature 'gradient*.