smaller proportional number of deaths under thirty and forty than either of the other classes. It is also worthy of observation that the per-centage proportion of deaths from consumption under thirty and forty is higher in the class of tradesmen than in that of the artisan and labourer, although the ratio of cases of consumption is greater in the latter class. This is doubtless accounted for by the fact already established, that the strong exertion which a considerable portion of the labouring class employed within doors use in their occupations, and the large number employed out of doors, has the effect of retarding the effect of pulmonary consumption. The tradesman, it will be seen, occupies the intermediate place between the indoor and outdoor labourer—between the artisan using little exertion and the artisan using much exertion.
... Another point attracts attention, viz. the great proportion of deaths from consumption occurring in the class of gentry from fifteen to twenty years of age. Does not this show that the liability to the disease is greater in this class than in the two others, and does it not tend to strengthen the position that the
excess of the deaths from consumption in the other classes is due to the unfavorable circumstances in which they are placed?
“The ratio of deaths from consumption in the class of gentry, low as it is, would have been still lower if the medical men, who are included in it, were omitted. The number of cases of pulmonary consumption occurring in members of that profession is very remarkable, and it is a subject of regret with the author that they were not made a separate class.”
Much less clearly and satisfactorily established is the question as to whether consumption is or is not contagious. The instances which have occurred of its extensive and rapid spread in overcrowded barracks, prisons, men-of-war, merchant vessels, large workshops, &c., not unreasonably seem to lend weight to the opinion that the germs of the disease might have been conveyed by the atmosphere charged with them from an unhealthy to a healthy subject, on whom they might develop the malady.
“But,” as Dr Blyth writes, “it must be remembered that, in all crowded localities, there is direct vitiation of air, and it is difficult to say whether the foul air or actual contagion have most to do with the propagation of the malady.” He adds “that consumption, under ordinary conditions, is certainly not contagious; but, under special insanitary influences, certain forms of consumption may be contagious, although it is still a matter not proven.” Dr Guy bases his objection to the doctrine of the generally contagious nature of consumption upon the fact of the small fluctuations in the annual number of deaths caused by it.
The lowest rate of mortality for phthisis for a million of inhabitants in London was, he states, for any one of the fifteen years from 1840 to 1854 inclusive, 2645, and the fluctuation was very slight. The figures in three consecutive years were—1849, 2777; 1850, 2645; 1851, 2970. “If, then,” Dr Guy says, “any one were to assert that this disease is contagious, which is tantamount to saying that it may be epidemic, the figures I have quoted would in themselves furnish an answer in the negative. They are suggestive of a domestic disease, influenced, as is bronchitis, by the seasons and the weather.”
The statistics before quoted as to the correlation between the prevalence of consumption and unhealthy surroundings, lead to the belief, that before this connection between the two was so well defined, cases of phthisis were often erroneously referred to hereditary taint, when they may simply have arisen from the patient having been environed with the same unfavorable hygienic conditions as his parents; these unfavorable conditions, including not only polluted air, but bad food, deficient apparel, and want of exercise. Hence it is that most of the later pathologists, without denying the existence of the transmitted form of the disease,
believe the hereditary influence has been greatly over estimated.
“As regards the origin of tubercle,” writes Dr Douglas Powell, “opinions are extremely various, and indeed irreconcileable; but the tendency of modern research—the experiments of inoculation in animals, and the very powerful advocacy of Prof. Niemeyer, is certainly to show that tubercles is much more commonly a secondary disease than has until lately been suspected—that people are, in fact, only exceptionally, if ever, born to die of tuberculosis.