As regards appearance there is great diversity in the protuberances we have given the prosaic name of scrotum. Scrotums may be large or small, long or short, smooth or wrinkled, heavily or lightly pigmented, nicely rounded or extremely asymmetrical. In fourteenth-century Europe high-ranking nobles were allowed to walk around with naked genitals under their short tunics. Their tight-fitting short breeches were not closed at the crotch. If their private parts were not sufficiently large to dangle about alluringly, they wore a braquette, a set of simulated genitalia in leather. Later, in the fifteenth and sixteenth centuries, another ornament came into fashion, the so-called codpiece (cod means scrotum), which was sometimes embroidered or encrusted with jewels. It was a final relic of the age of chivalry, and today’s double-stitched fly may be the last of the codpiece.
The left testicle usually hangs slightly lower than the right. This has nothing to do with being left — or right-handed. The anomaly is probably due to the fact that in most men the left testicle is slightly larger and heavier than the right. As a result the penis also usually ‘hangs left’, as the saying goes.
Until quite recently tailors making a bespoke suit asked their customer whether he ‘dressed left or right’, so that extra material could be sewn in to camouflage as far as possible the effect of dribbling after urination. The modern clothing industry certainly also takes this into account: the better makes of menswear cut the front of the left leg of a pair of trousers three-quarters of a centimetre wider as standard!
Apart from that, opinions differ on whether the scrotum couldn’t have been made slightly more appealing in appearance and on whether the positioning of the scrotum couldn’t have been a little more convenient, certainly in an age when cycle sports are exceptionally popular. After all, in many animals the semen-producing organs are tucked neatly into the abdominal cavity. In rodents and prosimians, for example, the testicles descend only in the mating season and subsequently return to the abdomen. This is not the case in man or in his oldest domesticated animals. Recent research has shown that the positioning of the testicles is mainly connected with the lifestyle of the species. This actually undermines the ‘balls-as-coolbox’ theory (of which more below). Animals that move fluidly have their sperm — factories enclosed in their bodies, while those that run, jump, jolt and bump, were better off with testicles located externally.
Long before birth the testicles and epididymides are formed in a place at the back of and high above the abdominal cavity, in the vicinity of the kidneys. From there the testicles descend down a kind of slide formed by the back of the bulging abdominal membrane, towards the inguinal canal at the bottom of the abdomen. If everything goes to plan in the last three months of pregnancy the testicles and accompanying seminal ducts and blood vessels descend through that inguinal canal into the scrotum. The above explanation is not totally accurate, since in fact the testicles gradually move lower and lower as the body grows lengthways. Be that as it may, in approximately 95 per cent of ‘full —
term’ males the testicles are in the appointed place around the time of birth. It may happen that the testicles remain within the abdomen. When this occurs in a male pig the animal is known as a ‘cryptorchid boar’ or sometimes, more colloquially, a ‘rig pig’.
A true cryptorchid boar takes at least ten minutes to complete ejaculation of his sperm — two coffee mugs full, containing as it does over 8o billion spermatozoa. In mating a zebra stallion may ejaculate as much as 300 millilitres of sperm, that is, over a quarter of a litre. After being mounted the mare appears to urinate, but in fact this is part of the seminal fluid flowing out of her body. A man discharges between 2 and 4 millilitres at each ejaculation. To put things in perspective, the volumes of a number of other animal species are as follows: bats 0.05, foxes 1.5, dogs 6, domesticated donkeys 50, domesticated horses 70, domesticated billy-goats 1 and turkeys 0.3 millilitres.
The male actually owes the scrotum to his female origin. It is only at the moment when it is decided that the embryo is to continue its development as a male that the embryonic labia grow together to form the scrotum. One has only to look closely: right down the centre of the scrotum runs a line of raised skin, the scrotal seam.
According to some experts, there is a good reason for the positioning of the testicles outside the abdominal cavity (though dissenting voices will also be heard in this book). The first group see the normal body temperature of between 36.5^ and 37°c as too high for the
efficient production, maturation and storage of healthy human sperm cells. That is the principal reason why nature has opted for a location in the cool-box that we call the scrotum, where the prevailing temperature is between 33 and 34 degrees. One way in which this cool-box operates is through vascular temperature regulation: the artery supplying warm blood from the abdominal cavity is quite convoluted just above the testicles and is surrounded by a complex network of vessels called the plexus pampiniformis. This network transports cool arterial blood from the testes back towards the heart. That colder blood washes around the main artery and ensures that the arterial blood flowing to the testicles is cooled so that it cannot harm the young sperm cells. The fact that testicles need protection from both excessively high and excessively low temperatures is evident from a feature that in our modern society benefits only inveterate naturists: the strong pigmentation of the skin of the scrotum. This dates from when primitive man wandered around the African savannahs without protective clothing. A dark skin after all offers more protection against sunlight than a light one. But too low a temperature is not good either! Every man who walks into the sea from a warm beach knows this: the cremaster muscles instantly lift the testes back towards the warmer groin.
The location of the testicles outside the body was therefore probably designed to protect the reproductive cells from extremes of temperature. However, one further safety measure was put in place, namely the so-called blood-testicle barrier. Sperm cells are very unusual, in more than one respect. They are haploid, that is, they contain only one copy of our genetic material. All other cells are diploid, containing a copy in duplicate of hereditary characteristics. Such diploid cells are regarded as malignant intruders in the testicles. By its own logic the immune system has an irresistible tendency to attack anything with the characteristics of a sperm cell. This is why the blood-testicle barrier, with the aid of a membrane and special Sertoli cells, seals off the sperm-producing tubes from diploid body cells. If this line of defence is breached the man will start producing antibodies against his own spermatozoa.