We pass on, Gentlemen, to another and most important branch of our subject.

I must now speak more at length of those states of health to which I referred in my second Lecture, when I said that I should impress upon you that "they are intimately related to the definitely marked diseases" - those states so puzzling to the young practitioner, because they do not fall under any of the nosological headings which have been his landmarks in the study of disease - those states which, although perhaps familiar in their aspect to most old practitioners, are, nevertheless, most inefficiently treated, or not treated at all, because their interpretation is so little understood, and because their importance is not appreciated; conditions which are not recognised as disease, but which certainly are not health, and which I propose to class under the general heading of "Abnormal Physiological States." I will give you some examples of what I mean.

A family of four children were exposed to the infection of measles at the same time, and from the same source; all of them were supposed to be in health at the time. One had the measles simply and slightly; one had a severe attack of pneumonia combined with it; one indicated a disposition to typhoid symptoms, and was completely oppressed by the morbid poison; a fourth lingered in convalescence, and was found to have become the subject of a deposit of tubercles in the lungs.

A party of friends, all apparently in what is called health, met at a funeral: they went together into a damp, unwarmed cemetery chapel on a raw winter's day, and returned together, one and all complaining that they had taken "a severe chill." They dined together, and went to their homes. One suffered an attack of rheumatic fever; one had anasarca; one jaundice; another bronchitis; a fifth pneumonia; a sixth diarrhoea; a seventh had erysipelas; and another had pleurisy. One coughed up a quantity of blood; while the rest got a restless night, and a cold in the head, and thought no more about it. These are no imaginary stories; analogous cases frequently occur within the experience of medical men in large practice. But what is their interpretation? Why did the same cause - the chill - produce such different effects, under external conditions, apparently the same? No doubt, the first answer which suggests itself is, that the circumstances, so apparently the same, must have been really different. Well, gentlemen, I will admit that, as the first step towards solving the difficulty. But I will insist that in a given case, the cause, so far as the chill is concerned, shall be the same in each individual; and the circumstances, so far as they are external, shall be the same for each individual. Nevertheless, these different effects shall be produced; and the reason we shall find to be this, that there are other causes and other circumstances, different in each case, existing within the organisms of the sufferers, with which the one cause - the chill - has to combine in producing its effect, and that the effect is the result of this combination of causes, different in each individual.

Some of you, perhaps, will say that this simply means that the different effects are explained by the different idiosyncrasies of the individual. And I must warn you against adopting a word as the explanation of a difficulty, lest in doing so, you fail to investigate the multitude of facts which that word may represent. I have no objection to the word, so long as you bear in mind that you must be able to explain what it means, if it is to be accepted as any explanation at all. Professor Bernard has spoken well on this subject: "I discovered," he says, "that section of large divisions of the sympathetic nerve was apparently unattended with the slightest inconvenience, as long as the health of these animals (rabbits) remained perfect, but as soon as a general debilitation of the system arose from want of proper nourishment, acute inflammation was produced in the organs deprived of nervous influence. We had, therefore, succeeded in artificially creating particular idiosyncrasies in these animals, and could predict with certainty that, as soon as health failed, disease would arise at a given point. Morbid predispositions must, therefore, be viewed in the light of peculiar physiological conditions." And he concludes thus: "Let me advise you not to consider idiosyncrasies in the light of mysterious powers residing within the depths of our organs, nor as entirely novel functions superadded, as it were, to those which already exist. They must be viewed as mere manifestations of the ordinary laws of physiology." - (Bernard, Lecture V., "Medical Times and Gazette.")

Health, gentlemen, is the normal physiological state; and peculiarities in, or divergencies from this condition must be regarded as greater or less deviations from health (abnormal physiological states) in proportion as they predispose to contingencies which increase the probabilities of death before the normal term.

There are very few persons who pass through life in the normal physiological state. At some period of life almost every individual diverges, more or less, from this state in one direction or another; and during that divergence, although escaping an attack of what is recognised as disease, he certainly is not in health; and in almost every individual there is a tendency to diverge in some particular direction, during which divergence - i.e., during that period of deranged health - he is particularly prone to certain classes of disease. In the case I have taken as an example of the effects of chill, for instance: - the man who had rheumatic fever was already surcharged with acid. He who had jaundice was suffering from defective excretion by the liver, requiring only a certain increase in the defect, or of the demands upon the excreting function, to throw the secretion back into the blood. The patient who had anasarca was suffering either from hydrsemia, or from defect in the excreting powers of the kidneys. The sufferer from bronchitis I attended myself; he had chronic congestion of the bronchi, from repeated former attacks of bronchitis, and the circulation through his chest was defective, from a feeble, degenerated heart; but he had been accustomed to pass as a man in health, competent to perform the onerous duties of a tax-collector and county-court agent. He who had an attack of diarrhoea, found in his bile ducts or in the intestinal mucous membrane a safety valve, by which he was saved from either anasarca, jaundice, or rheumatic fever.