The two

occasional complication of phthisis. conditions are certainly not incompatible, although I believe that the one modifies the developement of the other. It is not improbable that the diminished quantity of blood in emphysematous lungs may lessen the chances of tubercular deposition in these organs, by circulating within them a proportionate small amount of tuberculous material. But in whatever way it be explained, it is certain that emphysema, although it may, and generally does, greatly aggravate the patient's sufferings, nevertheless tends to make the tubercular disease more chronic, and greatly to retard the fatal issue.

The skin of the face, chest, and arms of consumptive persons occasionally exhibits the coloured patches known as ephelis, but I cannot give its numerical frequency: this, however, is scarcely to be considered a disease; and the reason why it may, perhaps, be oftener seen in phthisis than in other affections, is, on account of its being particularly visible in the usually delicate skins of scrofulous persons.

In conclusion, I would repeat my belief that there is no disease which can properly be said to afford immunity from consumption. Both the constitutional and local symptoms of phthisis may coexist with any other morbid condition; but from the general law already adverted to, of the little tendency in the body to carry on, simultaneously, two dissimilar morbid actions, the complications of phthisis are few and uncertain.

CHAPTER IX.

CAUSES OF CONSUMPTION: PREDISPOSING AND EXCITING.

PREDISPOSING CAUSES.

THERE are many circumstances which influence, in different ways, the developement of consumption. Some of these act by rendering persons more liable than they would otherwise be, to its attacks; whilst others have a more direct effect in immediately producing the disease. Hence, the causes of phthisis have been divided, like those of other diseases, into two kinds, viz., predisposing and exciting; a distinction which will be found useful, and, in the majority of cases, strictly practical, although the modifications to which they are liable may sometimes render it difficult to define the operation of either, or to separate that of one from that of the other. The occurrence of both, or rather the sequence of one to the other, is, moreover, not always necessary to the production of the malady; that is to say, either of them may, under peculiar circumstances, unite in itself the action of the two. Examples of this may be seen in members of a family strongly affected with hereditary consumptive pre

disposition, dying one after another, in spite of the most careful avoidance of exciting causes; and again, in certain cases where, in consequence of some febrile or inflammatory attack, which more usually would be considered an exciting cause, persons, previously in good health, and, so far as we could judge, very unlikely to become consumptive, suddenly fall a prey to rapid phthisis.

The predisposing causes of consumption include every circumstance and condition of life which at all favour the developement of the disease, but which are insufficient, except in a few cases and for special reasons, solely to give rise to it. Of these, age, sex, stature, constitution, temperament, hereditary transmission, occupation, climate, habits of living, and mental condition, are the chief; and bearing, as they do, a very unequal share in its production, require to be considered separately.

Influence of Age.-No period of life is exempt from phthisis; infancy, youth, manhood, and old age, are liable to its visitations; and it has even been met with in the fœtus. The tendency to it varies, however, with the age, as may be seen in the next table, derived from cases which have fallen under my own observation.

A glance at this table shows that the disease is most frequent between the ages of twenty and thirty, -more than 39 per cent. having occurred within this period: that the next age most favourable to its developement is from thirty to forty years; that the

next to this is from ten to twenty years; and that after the age of forty its frequency gradually lessens, until, as we approach the "threescore years and ten", few cases present themselves. There is a prevalent idea, but obviously an incorrect one, that after having passed the meridian of life we become exempt from consumption;—the table showing that the disease is not infrequent up to the age of sixty, and that, even after that, it is far from being unknown.

TABLE III.

Showing the Ages of 1000 Persons in various Stages of Phthisis; namely, 582 Males and 418 Females.

It is important to observe that the greatest liability to phthisis occurs at the very time of life when causes which will be shown to predispose to it, are most energetic. At the age of from twenty to thirty, the mind has begun to exert a new and untried action upon the functions of the body; the prospects of youth have become realities; anxiety and care exercise their influence; evil habits also often originate or become confirmed; until the health fails, and the system is unable

longer to cope with the hereditary germs of disease, or resist that tendency to their production which is common to us all.

The following table, deduced from the preceding one, is added, in order to exhibit the influence of age, as modified by sex:

Thus females, up to the age of thirty, are shown to be more liable to phthisis than males of the same age; but after that time, the disease is much more frequent in the male sex. The circumstance that a very similar observation is to be found in the statistical records of the Hospital for Consumption,* furnished by my colleagues and myself, gives additional importance to this statement. Why it should be so is, perhaps, difficult to explain satisfactorily; but, possibly, a reason may be found in the circumstance that, in large towns

* Medical Report of the Hospital for Consumption, 1849.