The scrotum is a bag of loose skin containing the testicles which is suspended from the perineum behind the penis. The testicles are suspended outside the body since they are meant to function at a temperature below that of normal body heat. If they are overheated by hot baths, electric blankets, tight underpants, etc. spermatogenesis stops and over a long period of time this is one of the commoner causes of infertility in the male. The skin of the scrotum is loose and particularly well equipped with sweat glands which enable it to maintain the testicles at the correct temperature by a process of constant evaporation and water loss. The wall of the scrotum also contains the cremaster muscle which contracts if the outside temperature is unduly cold and draws the testicles up towards the body, thus maintaining them at their functioning temperature.