conclusion respecting it must be received with some degree of qualification; but the facts I have gathered, warrant the belief that there exists no special relationship between the syphilitic poison and the formation of tubercle.

A similar observation would, perhaps, apply to every other disease, with the exception of diabetes, which is well known frequently to terminate in consumption, and this even in cases where no other predisposing cause is discoverable.

The medicinal use of mercury has been sometimes accused of acting as the predisposing agent to a subsequent developement of consumption; but I have never met with a single instance where the commencement of this disease was fairly attributable to such a cause. Persons who have suffered in health through the use of this remedy, doubtless, often become phthisical; but I believe that in these cases it is seldom the mercury which has caused the mischief, but rather those vicious habits which, in the majority of such instances, have made its employment indispensable. The real sufferers from mercurial action are those whose diseases have been self-inflicted; for it does not appear that the proper use of this medicine in the ordinary class of inflammatory affections, is necessarily followed by injury to the health; and there is still less reason for ever attributing to it the origin of phthisis. It is, indeed, a truth which ought many times to have spared our art unjust

discredit, that there is nothing in the specific action, either of mercury or of any other medicine, at all calculated either to predispose to, or excite tubercular diseases.

I am

The form of the chest, in its relation to the phthisical diathesis, requires to be referred to, since peculiarities in this respect have been generally classed amongst predisposing causes. satisfied, however, that the shape of the thorax has very little to do, primarily, with the developement of consumption; for it is equally common to see phthisis attacking persons of fine and well-proportioned chests, as those who are the subjects of some congenital or acquired thoracic malformation. The life-guardsman, the pugilist, the blacksmith, etc., notwithstanding the fully-developed chests which their several occupations induce, are, in fact, cæteris paribus, quite as liable to the inroads of phthisis as the mechanic or artizan, whose daily task leads to the opposite result. Continued observations upon phthisis, in all its multiform characters, have led me to the following conclusion :— that the best formed chests afford no security against the onset of the disease; whilst those which are comparatively ill-developed, or even deformed, do not appear the more liable, on that account, to become the seat of tubercle.

We have thus seen how the predisposition to phthisis may be either inherited or acquired. There

is usually a marked difference in the course of the disease according as it owes its origin to one cause or the other; cases arising from hereditary taint, being, for the most part, more intractable, of shorter duration, and less amenable to remedial agents, than are those in which the tuberculous diathesis has, from any cause, been acquired. The reason of this is obvious. In the one instance we cannot separate the patient from the cause of his disease, but, in the other, this very frequently can be accomplished. Hence, in forming the prognosis of any particular case, this point should be always taken into consideration; the answer to the question, -whether or not other members of the family have been consumptive,-enabling us, very often, to form a more correct opinion as to the probability of our treatment proving successful.

Before closing this chapter, it is necessary to observe, that some of the circumstances I have included amongst the predisposing causes of phthisis, have been thought by others more plausible than demonstrable. I am, however, far from asserting, that even the most potent of them must, of necessity, lead on to consumption; for it is evident that one person may bear with impunity that which to another might be highly prejudicial. Every conclusion respecting the effects of a number of very different and variously combined agencies, upon anything possessed of such unbounded diversity as the human body, cannot be other than of a general

character, and must ever be open to numerous exceptions. But I doubt not that those whose opportunities of observation upon the various causes of this disease have been extensive, will readily admit the influence, although in different degrees, of the several conditions which I have thus attempted to describe.

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CHAP. IX.

EXCITING CAUSES.

ANY severe or long-continued consumptive predisposition may develope the disease without the supervention of an exciting cause; this we see exhibited in certain cases where either the hereditary taint, or the acquired morbid state of nutrition, is sufficient, of itself, to produce the tubercular substance. One predisposing cause, also, supervening upon another, may act the part of an excitant; thus, an hereditary tendency may be brought to light in consequence of unhealthy occupation, or mental distress, or by something which has reduced the general vigour of the system; and to this mode of origin a vast number of phthisical cases are manifestly due. But it often happens that something of a more active kind, but which, in the absence of pre-existing liability to the disease, would have had no such effect, has led to its developement; and it is this which constitutes what is usually understood as the exciting cause. Certain inflammatory conditions of the chest, catarrh, influenza, fever, pregnancy, lactation, etc., have more or less influence in this way, and therefore require to be noticed separately.