BEFORE making in the next three chapters a comparative study of the excretory function in the three different cases, we must state here at once, that although the excretory mechanism is the same, the excreted material is entirely different in the three cases. We shall, at the same time, enquire in every instance how far we have to do with a glandular secretion.
Firstly, the intestinal contents. The intestinal contents consist of a mixture of waste products and glandular secretions. The gut contains all gaseous, liquid and solid waste products of the food we have taken in, substances that have not been absorbed, but are simply expelled after passing through the alimentary canal. The lower portion of the intestine moreover contains large quantities of the bacteria which have been of service in the process of digestion. Further, the gut contains the whole of the secretory products of all the digestive glands, from the microscopic gastric and intestinal glands to the large glands, such as the liver and pancreas. Next to the food-residue, the products of this glandular secretion are quantitatively very considerable. This is clearly shown by the fact that at birth, faeccs are passed, although the newly-born child has never yet taken any food, unless perhaps it has swallowed a little of the “waters” (liquor amnii). Finally we find in the gut as well as in the other excretions, numerous dead epithelial cells and much mucus; both derived from all the mucous membranes of the gut and of the gland-ducts.
Owing to the admixture of food-residue, the evacuations of the gut are called excretions instead of secretions. This distinction is, however, not as important as appears at first, for if only wholly digestible food-materials are taken in, such as rice, sugar, butter, roast-beef, etc., the food residue almost entirely disappears. The color is derived from the bile. As soon as the supply of bile is cut off, the faeces become colourless.
The odour is that of putrefactive processes, and may, therefore, be made almost to vanish by the daily consumption of Yoghurt (a bacterial preparation of milk first introduced from Bulgaria). But the smell of any substances accidentally mixed with the food, such as sulphureted hydrogen compounds after the ingestion of sulphur or onion, remains unaltered.
The volume of the faeces is more or less proportional to the food residue, but depends even more on the water content, which is sometimes very small, but may at times be excessively great so that the intestinal contents may become quite liquid.(1)
Under the influence of some drugs, e.g., Epsom salts, and some diseases, e.g., cholera, the excretion of water by the intestine may considerably exceed that by the kidneys. The excretion of the contents of the bowel is dependent above all on the volume of the contents. Here, as in the other two excretions, the mechanical pressure produced by over-distension stimulates contractions in the muscular walls, at the same time the irritability of the intestine may he either morbidly increased or diminished.
Secondly, the urine. The urine is a typical glandular excretion, a waste product of the glandular cells of the kidneys. Since, however, the cells of the kidneys are very well supplied and nourished with blood, the urine also contains the main portion of the liquid waste products of all our tissues and organs in so far as they are introduced into the circulation by means of the lymphatic system.(2)
These products of metabolism are in the first instance those of the muscular tissues, which perform our mechanical work. It is therefore hardly to be wondered at that the smell of the urine, when no food is taken that might influence it, is rather like bouillon, even if no meat has been eaten.
If, for example, small traces of oil of turpentine are swallowed or even only inhaled, the urine will assume a pleasant odour of violets. In ancient Rome, the ladies of the demi-monde did this on purpose, and they took a little belladonna (hence the name) as well, so that the pupils of the eyes should become as large as possible.
The production of urine varies in quantity with the rate of metabolism, and especially with the blood pressure. The blood pressure and the secretion of urine can be artificially increased by all kinds of stimulants, for instance through the consumption of strong irritant drugs like alcohol, hops, cantharides (Spanish fly), oil of turpentine, balsam and many ethereal oils and condiments.
The production of urine is indispensable for the continuation of life, on account of its vital importance in purifying the blood.
Finally we come to the sexual secretion. As the bladder periodically expresses the urine by means of muscular contraction of its walls, so likewise, by energetic contractions of their muscular walls, the seminal vesicles and ducts of the adult discharge periodically a few drops of mucous liquid-the semena turbid viscous fluid like a thick gruel, which soon becomes more liquid when exposed to the air.
This is neither a solid substance as in the gut, nor a watery solution, like the urine. It has the typical character of an emulsion. Just as milk is an emulsion of microscopic globules of fat swimming in a colourless menstruum and blood an emulsion of microscopic red corpuscles swimming in a colourless menstruum, so the semen is an emulsion of microscopic sperm-cells swimming in a colourless menstruum, mixed with a quantity of mucus derived from the mucous membrane of the seminal vesicles. Besides this mucus the semen contains a few crystals and a number of dead and degenerated epithelial cells derived from the genital canal. The colour of the semen is between that of milk and that of water, and the smell is stale and something like decomposing leeks. Further, the reaction of the semen is neutral and it is salty like ,tears or bloodserum.
The innumerable young vigorous new-formed cells derived from the testes form by far the most important part of the semen, though quantitatively only a small percentage of it. Thus it is not so much a case of glandular secretion as of a quite peculiar new-formation, as we have already pointed out in Chapter 2. As in the case of the secretion of urine, the energy with which the secretion is ejected does not depend so much on the composition as on the quantity, i.e., the overdistension stimulates the muscles to contract. Here again we have to consider the varying sensitiveness of the organs to irritation, and the degree of irritation to which they are subjected.
Thus there are cases in which the apparently normal secretion contains no sperm-cells (azoospermia).(8) This often happens after recovery from gonorrhea, if the two narrow sperm-ducts are completely closed by the contraction of the scar-tissue in the process of healing; also after operative procedures, for instance vasectomy, i.e., the intentional interruption of the continuity of the two sperm-ducts. If this occlusion or interruption of continuity takes place in adult life, when the seminal vesicles are already accustomed to secrete mucus, this secretion of mucus without admixture of sperm-cells can go on as before, and indeed with all its normal attendant manifestations of congestion, erection, desire, voluptuous sensation and satisfaction. If, however, the two testicles have been removed, especially in childhood, then not only will the ejaculation contain no sperm-cells, but the organochemical matter mentioned in Chapter 4 which gives rise to the normal irritability of the adult nervous system will be absent from the blood-stream. Such an individual is not only definitely impotent but is also defective in other respects.
Unlike the production of urine, the function of semen-production is not in itself an essential condition for the preservation of life. All of us have lived through childhood without producing semen, so an adult can remain alive with little or no production of semen, especially in advanced years. But when once the seminal vesicles become distended, they will empty themselves as in the case of the bladder, either with or without our conscious consent.
The female, genital apparatus is more economical, both as regards the number of cells expelled and the periodicity. At menstruation, generally only a single unfertilised ovum, something like an abortion, is expelled together with a large amount of blood and mucus derived from the excretory tract, and with a number of dead and degenerated epithelial cells, At the beginning and the end of menstruation, mucus preponderates, during its middle period, blood. In the seminal secretion of the male, pinkish traces of blood may also occasionally be found, but they are of no importance. In the same way, in catarrh of the mucous membranes of the bladder and bowels, the mucus may be more or less tinged with blood, especially in infants and young children. It is not improbable that originally in carnivorous animals this greater amount of blood in the female secretion had a certain significance as a sexual lure in the struggle for existence. It also made the sexual act easier at that time when this discharge of blood was still a principal factor at the rutting period.
Apart from this sexual secretion, a small drop of mucus derived from the genital canal may be excreted, by the woman from the mouth of the uterus, and by the man from the orifice of the urethra, during sexual excitement; this is of no special importance as long as the drop is as clear as water. It is often merely an expression of voluptuous feeling. If this drop of mucus in the man or of vaginal discharge in the woman is turbid and milky or purulent, it means in the man certainly gonorrhea, in the woman possibly gonorrhea, but in most cases only leucorrhea, or “fluors albus,” which the French politely call “fleurs blanches” instead of “flueurs blanches.”
Such a catarrhal discharge from the female genital tract may be comparatively harmless, containing only putrefactive bacteria, but it may also contain pathogenic germs, even those of a contagious disease, for instance gonorrhea. So it is much easier to make a mistake in the diagnosis of this disease in the female than in the male. The latter notices it early because milky and purulent drops escape from his meatus (hence the name gonorrhea = flow of semen which was given to it in error). These drops leave starch-like traces on the linen in drying. Violent pain and burning on micturition and on erection induce him to consult a doctor. Actually, each day’s delay makes this disease of the mucous membrane more difficult and More tedious to cure. For this reason even a very slight infection in which the discharge is at first hardly noticeable, and only turbid, like soapy water, may often give rise to the most unfortunate results. In the woman this disease is as we have said, generally unrecognised in its initial stages, and for this reason it is a prolific source of innumerable genital abdominal diseases and of sterility.(4)
While man only gets a urethral discharge by infection with virulent gonococci, woman, probably on account of the width of her genital tract, is much more prone to fluor albus on the slightest provocation, the vulva and vagina being so easily accessible to even the mildest infection. Moreover, the possibility is greater because most women and girls omit external and internal cleansing after each menstrual period, so that the resistance of the mucous membrane is soon lowered.
In conclusion, if we consider these secretions which were formerly regarded as waste matter, it is not surprising to find that the microscopic cells, which are by no means waste matter, but on the contrary new-formations, have only recently been recognised as importantlike pearls in a mass of mud.
It was not till 1677, in the days of the famous microscopist Leuuwenhoek, that a Dutch student at Leyden, named Lodewyk van Ham, discovered the sperm-cells, which he called spermatozoa. Swammerdam, who died in 1685, rightly conjectured that contact of an egg-cell with these spermatozoa gave rise to fertilisation. The human ovum was not discovered till 1827, by C. E. von Baer, and only in 1850 did duBarry succeed in actually observing the penetration of a rabbit-ovum by a sperm-cell.
1 In taking a medical history it is usually wise to inquire into the consistency rather than the volume, the latter being very often wrongly estimated by the patient, and necessitating a further examination, a task one would rather dispense with for one’s own sake as well as the patient’s.
2 Solid substances are at first not contained in the urine. The gaseous end-products of our metabolism are excreted by the lungs.
3 A symptom that has nothing in common with impotence. One can only speak of impotence when erections are lacking, for instance in paralysis of the external occlusory muscles.
4 Luetic (syphilitic) infection, on the contrary, often causes a series of miscarriages.