The development of the testis, epididymis, and penis in the young Merino ram

Abstract

Observations were made on 110 Merino rams aged between 1 and 64 weeks. They comprised four groups, the animals of which experienced different rates of growth. The weight of the testes a t any one age varied widely. It was closely related to body weight. This relation was similar in all groups. As body weight increased from 23 to 27 kg, the relative increase in the weight of the testes was much greater than that a t higher or lower body weight. The general histological characteristics of the testes were closely related to their weight, and, like it, to body weight. The tubules were present as solid or but slightly vacuolated cords in all animals which weighed less than 21 kg. Spermatozoa were not seen in the lumen of the tubules in any animal which weighed less than 27 kg, and they were present in all but three of those which weighed more than 28 kg. The relative cross-sectional area of the seminiferous tubules increased directly with the relative increase in the weight of the testes until the testes weighed at least 300 g. The weight of the epididymides was more closely related to the weight of the testes than to age or body weight. Its relation to the weight of the testes varied in the different groups. Irrespective of the age a t which the particular body weight was attained, little separation of the prepuce from the penis had occurred in animals which were lighter than 18 kg, and separation was more or less complete in most animals which were heavier than 27 kg.