The volume of a testicle can be estimated by using a tape measure and comparing the readings with plastic models of known volume. For adult men the volume usually exceeds 15 millilitres. A volume of between 17 and 25 millilitres is regarded as normal. The length varies from 3 to 6 cm, the width from 2 to over 3 cm. Large or small, these glands constitute an extremely ingenious production unit which every day turns out between ten and a hundred million ‘homunculi’, or tiny male creatures.
The volume and firmness of the testicle may indicate whether there are any endocrinal abnormalities. Small, rubbery testicles in a grown man, for example, may indicate insufficient stimulation. Before puberty the testicles are small, but the absence of a testicle from the scrotum is abnormal. It may be a case of a retractile testicle caused by the tensing of the testicular muscles, whereby the testicle is pulled in the direction of the external inguinal opening or even the inguinal canal. The medical term for this phenomenon is the cremaster reflex, which causes the sudden disappearance of the testicle!
The cremaster reflex may be triggered, for example, by stimulating the skin on the inside of the upper thigh. In older men the reaction is harder to provoke. The spiral-shaped fibres of the cremaster muscles run through the seminal cord to the base of the penis and when suddenly contracted may even result in testicular torsion. On the underside the testicle is attached to the scrotum by a wide band which normally prevents it from it turning vertically on its own axis.
During sexual arousal engorgement with blood causes the testicle to increase in volume by up to 50 per cent. In the case of prolonged sexual arousal the accumulation of blood may cause pain (‘blue balls’), from which ejaculation brings relief. (Not that women should feel in any way responsible for this state of affairs!) Scientists in the German state of Thuringen were able to demonstrate that when the testicles of male ferrets swelled in spring, their brains also increased in size — definitely not the case in humans!
Moving balls also seem to be an object of particular fascination for visual artists. Joop van Lieshout, for example, has produced a series of huge plastic penises, and in a tv programme he showed an excerpt from a work by his fellow-artist Bruce Nauman, who in 1969 filmed the dangling and bouncing of his own testicles with a high-speed camera, as part of a series of four Slo Mo films: Black Balls, Bouncing Balls, Pulling Mouth and Gauze.
Nauman hired an industrial camera to film at very high speeds: the frame speed varied from 1,000 to 4,000 per second (the normal speed is 24 fps), in natural light. The shooting time was between four and six seconds, but the running time of Bouncing Balls is nine minutes. The extreme slow-motion effect means that movement is sometimes scarcely perceptible.