The loss of water, in cholera patients, has hitherto solely been considered with respect to the injury the blood thereby sustains; it can, however, be shown that this loss constitutes a source of nervous irritation and consequent muscular contraction. Withdrawal of water from the nerves, if performed either gradually or with extreme rapidity, produces no effect, but if performed with moderate rapidity causes tetanus. The longer the portion of nerve exposed to desiccation, the more violent the tetanus. The contractions of the muscles being when the nerve has lost about 4 per cent. of its weight and its excitability is lost when about 20 per cent has evaporated, The sudden deprivation of water from the nerves may perhaps account, in part at least, for the spasms of cholera.(*Carpenter’s Human Physiology, 9th Edition, P.550*)
There is then a connecting link between choleraic discharges and the contractibility of the muscular coat of the arteries with its subsequent venous congestion, the cramps of the extremities, the colic-all may be traced to the constant loss of water. Besides the effect the withdrawal of water has, upon the nerve tissue, there is another effect produced on the nervous function. Excess of pressure is known to arrest nerve action. When on the other hand the normal pressure upon the nerve substance is diminished, we may infer, that nerve action will be immoderately intensified. This explains why cerebral anaemia which means comparative emptiness of the cerebral blood vessels, and consequently comparatively diminished pressure of those vessels upon the adjacent cerebral mass, produces cerebral irritation manifested by convulsion. We are all more or less acquainted with that peculiar nervous state known as irritable weakness. This irritability is caused not directly by insufficient nutrition but by insufficient pressure upon the nerve fibres due to the comparatively empty blood vessels. Something similar takes place in consequence of depletion going on during cholera and explains that strange phenomenon of exhaustion coupled with extreme restlessness.
In simple diarrhoea, even in the diarrhoea preceding cholera, however liquid and frequent the stools may be the molecular constitution of the nerves could hardly be affected in the way described above, for the patient is sure to replace the loss of water by drink. In cholera things are otherwise. One of the peculiarities of that disease consists in this, that the epithelial cells lining the mucous membrane of the alimentary canal are disorganised, if not actually shed altogether, so that assimilation, even by means of absorption is almost completely brought to a stand still. The desire for water may by no means be wanting; in fact the patient is often enough tormented by an unquenchable thirst; but the water drunk is either immediately ejected or it remains unabsorbed in the stomach till it is brought up during one of those fits of vomiting, which may repeat themselves from five to ten or thirty minutes, according to the virulence of the attack.
The pernicious influence, the deprivation of water has upon the state of irritability of nerve tissue, makes itself felt, as we have seen, in two different and diametrically opposite ways. The loss of a small portion of water (4 per cent.) causes nervous irritability; while a loss of 20 per cent. of the same fluid destroys its excitability altogether. This gives us a deep insight into what is going on within the patient during the algid stage of cholera, also called the asphyctic stage, or the stage of collapse. That this state is generally associated with a stage of deep depression of the essential vital functions-that vital energy is altogether at its lowest ebb, has already been stated before. It is however, commonly understood, that the exhaustion is due to the preceding nervous and muscular exaltation during the spasmodic stage; or to the loss of the nutrient materials contained in the serum; while there are no doubt cases and constitutions, where the whole nervous prostration and the subsequent collapse of the machinery of life is in the first instance due to the extreme desiccation of the nerve substance and the consequent inaptitude for action-far less for re-action. An ounce of water may be all, that patients thus affected may require, in order to come out of the desperate state they are in; and he, who will be able to make them retain it, may fairly be said to have saved their lives.
It remains now only to be shown, why of all the nerves of the body, the vaso-motor nerves of the pulmonary arteries are invariably affected in the way described, by the loss of water. In answer to this question we need only remember that we deal here with a specific poison, and that every such poison has its own particular toxicological affinities-affinities which are as unalterable as they are inexplicable.
I have gone a great length in order to show, however uniform cholera may be with regard to its final issue, it has at least two distinct points of attack, and that it is only at the stage of development that we see those two points moving toward one and the same centre of destruction. I have further endeavoured to trace the connexion which exists between the one mode of attack and the other and how the one rouses into action the other. Now from an absolute pathological stand-point all such considerations may be of secondary importance, since the pathological issue of the disease remains, in all cases, and under any mode of initial attack, the same; venosity of blood being, as I said before, the common characteristic speciality of all varieties of cholera. When we shall come, however, to the question of treatment, then we shall see the full importance of what has hitherto been said with regard to the two chief varieties of the disease under consideration. For what does it mean, that one and the same toxic agent attacks, during one epidemic, one man in the one way and the other in quite another way? Are we then to suppose that there are actually as many varieties of cholera-poison as there are varieties of the cholera disease? BUt then we know that even such uniform, inorganic poisons, as Arsenic for instance, assail different individuals in different ways. Toxicology teaches us then the grand lesson, that two persons may be in all physiological respects pretty much the same, and that they may nevertheless behave differently when exposed to the same toxic agent. We may then reasonably infer, when we see two patients differently affected by cholera, that the difference is to be sought in the respective individuality of the patients, and not in the cholera poison. And since the patient`s constitution, his individuality, and especially the peculiar relation which exists between him and the prevailing epidemic influence is to taken into consideration in our therapeutic proceeding it would be unwise indeed-if not even worse-to shut our eyes to all such pathological differentiations, to attempt to treat all cases according to a favourite term of a certain class of unprincipled physicians-on the same principle. Cholera may be the same in each case, but the patients are not the same with regard to the way how they are impressed by the noxious epidemic influence.
It is, however, not my intention to anticipate the treatment of cholera, which must be reserved for a future occasion; I shall, therefore, return for the present to such considerations as refer to the pathology and symptomatology of the disease under discussion.
You have heard, gentlemen, how the withdrawal of a certain proportion of water affects the nerves. There are, as far as I am aware, no records in existence of a similar experiment having been made with regard to muscular substance; we must, therefore, content ourselves with a vague conjecture about the subject. But although we may not be able to express in numbers the proportions of water which must be lost, in order to affect a muscle, it is evident that there must be a limit beyond which water could not be withdrawn, without interfering with the muscular function. Possibly there are two limits, as is the case with regard to nervous substance-a limit, beyond which all irritability is lost. Anyhow it is useful to bear in mind that, in the state of collapse, certain muscles may be thrown out of gear in consequence of want of irritability, while their respective motor nerves may still be in a normal state, or even in a state of abnormal excitement. This may explain certain states of a cholera patient, made up, as it were, of two opposite conditions. Take for instance, the muscular unrest of the patient along with its nervous exhaustion.
Then there is the elasticity of tissues, a most important element in the machinery of life, which must severely suffer whenever the organism is deprived of its normal proportion of fluids. Expiration is to a large extent carried on by the aid of the elasticity of the lungs. Donders estimates the expiratory force derived from the elasticity and muscular tension of the lungs, and coming into play in ordinary respiration, as equal to a pressure of about 5 ozs. to the square inch. It is evident that with the partial desiccation of the lung-tissue, a considerable amount of expiratory force must be lost. And last though not least, it is worth while to remember in some cases, the shock the system experiences in consequence of a sudden withdrawal of large quantities of so vital a fluid as the serum of the blood. I have seen cases where enormous masses have been brought up at the first onset of vomiting; the patient would then recline on his pillow in a state of syncope-half dead. Some of them would in an astonishingly short time regain the necessary strength for the struggle to come. Others, however seem to have received a death- blow from the very onset; they appear to be over-powered by the shock beyond recovery; at any rate, there can be noticed considerable failure of the heart`s action immediately after the first choleraic evacuations have taken place, without any tendency towards a gradual recovery of what has been suddenly lost in strength. Such patients may be considered as being in a state of collapse from the very onset of the attack.
