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CHAP. VII.

ON THE CONNEXION OF CERTAIN DISEASES.

It will probably be one of the most certain results of future inquiry to associate together, by the connexion of causes of common kind, diseases now regarded as wholly distinct in their nature, and arranged as such in our systems of nosology. This remark applies very widely throughout all the genera of disease; but in no instance so remarkably as to some of the disorders of contagious or epidemic kind; scarlatina, measles, hooping-cough, erysipelas, the infantile fever, dysentery, epidemic catarrh or influenza, &c. Without affirming the materies morbi to be the same in any two of these disorders ; presuming it to be different in most of them; - and admitting the diversity of the symptoms; yet relations there probably are, closer and more peculiar than any which have yet been ascertained, or made the basis of classification. And these form, without doubt, some of the most interesting objects of pathological research.

On the most general view of the subject, numerous conditions will be found capable of giving different aspect even to the effects of a common cause of disease. Season of the year; peculiar states of the atmosphere as to heat, moisture, weight, or electricity; circumstances of locality; the age of individuals exposed; their different temperaments; the influence of foregoing disease; the incidental direction of the morbid cause to some particular organ or texture of the body *;

* An illustration of this occurs in the glanders and button farcy of horses; the virus being proved by inoculation to be nearly, if not wholly, identical;

and still more the quantity or intensity of the virus itself: all these and other circumstances may be conceived as producing such modifications, and thereby concealing the common origin of many disorders. From this complication of conditions, the difficulties of inquiry are considerable, but still of a nature to be overcome by future observation.

Referring more especially to the disorders mentioned above, does it not happen that measles, scarlatina, hooping-cough, and infantile fever, are often singularly concurrent in particular districts, and about the same periods of time? And, as a variation of this fact equally illustrative, is it not common to find one of these disorders exceedingly prevalent in certain localities; while at the same time, in contiguous places, another of them equally prevails? Many instances to this effect come within my recollection; too strongly marked, as it seems to me, to be attributable to chance alone. Similar examples, though often indistinctly noted, are not uncommon in medical authors. If it be alleged that they prove only the influence of certain seasons and particular localities in evolving the virus of two or more of these diseases, or in creating a state of body favourable to their reception, still here are connexions which it is important to denote, and to follow into their several consequences.

Morton, as is well known, considered scarlatina and measles to be varieties of the same disorder. It would be difficult to

but affecting under the former name the lymphatics of the internal surface, under the latter those of the skin.

There is reason for the same inference as to the virus of hydrophobia; the variation in the effect of which on different animals may be presumed to depend, not merely on their diversity of habits, but also on the difference of parts more directly or more severely affected by this remarkable poison. The most exact observations we have on the subject are those by Dr. Wagner, in vol. i. of Hecker's Annals, 1836.

establish this opinion by any proof; and the actual points of diversity are indeed insurmountable; - especially the negative fact, that one disease has never been known by infection to produce the other; and the certainty that the infectious matter of each, though equally unknown to all observation of the senses, has different properties in relation not only to the human body, but also to other media, which are concerned in communicating the disease. Even the uniformity with which each disease manifests itself on different portions of the same texture- as the inflammation of measles on the mucous membrane of the air passages, that of scarlatina on the membrane of the pharynx-furnishes proof of different origin; and not less the difference in the character of the attendant fever, and of the sequelae of the two disorders. Yet still there are some relations which cannot escape notice; and which in fact lead to the occasional difficulty of discrimination, in the early stages, and in certain forms, of each disease. The case related in the subjoined note involves only a succession of the one malady to the other; yet this so singular, in having twice occurred under circumstances similar as to interval, as strongly to warrant the suspicion, that there was some state of constitution liable in common to both.*

who at the

* The remarkable case alluded to was that of Lord age of fifteen had the measles in the ordinary way, caught at a public school, when prevalent there. This was followed about two months afterwards by scarlet fever, with ulcerated throat: which went on in the usual course, leaving behind the most extensive anasarca over the body which I have ever seen in sequel to this disease; - cured by bark and steel, with blue pill and diuretics. Two or three years afterwards, Lord, when at Berlin, had the measles a second time. The physician who attended him in that city, entertained no doubt as to the nature of the disorder. And what forms the extraordinary part of the case, this attack of measles was followed again, after the interval of a few weeks, by scarlet fever, unequivocal in its symptoms, according to the information I received — with desquamation, but no anasarca following it. It seems impossible to

I have observed repeatedly that, during the seasons in which influenza has occurred as a general and severe epidemic, these two diseases of scarlatina and measles have been more than usually frequent; though in no instance, perhaps, reaching the extent to which they occasionally occur at other times:—and further, that during the actual prevalence of influenza, a class of cases has appeared of very singular and ambiguous kind, having many appearances analogous to each of these disorders, but particularly, as I think, to scarlatina. I noticed frequent cases of this nature during the influenza of the spring of 1833, when the scarlet fever was also very prevalent, and produced much mortality in London. A peculiar spotted efflorescence on the skin, generally attended with some angina, and occasionally with slight ulceration of the throat, were the symptoms chiefly marking this apparent relation; which was sufficient in degree to suggest the question, whether it arose from the concurrent action of two morbid causes; or from one virus capable of producing different forms of disease, according to the texture on which it fell, or other less obvious circumstances.* If hazarding an opinion on this obscure

suppose mere casual coincidence here; and I do not see any equivocal circumstances in the case, unless it be thought possible that what was deemed measles in each instance was merely an imperfect manifestation of scarlatina, followed by the more regular form of the disease.

* I have observed also many of these ambiguous cases during the yet more remarkable influenza prevailing while I write this note (Feb. 1837). In one singular instance, I traced something like a separate course of the two diseases in one family; two children having well marked scarlatina, with ulcerated throat, eruption, and desquamation, in a house filled with cases of influenza. It is worthy of note, that the symptoms of influenza in these children preceded those of scarlet fever by several days; and appeared distinctly to recur in succession to the latter, as a fresh seizure, after an interval of two or three days almost free from disorder. At the same time, two other children of the same family

subject, it would be in favour of the former view. Though we have many instances of such seeming incongruity of two diseases, that one present in the system precludes the ingress of the other, still there is no foundation for a general law to this effect. On the contrary, we have various proof that morbid actions, derived from sources wholly different, may co-exist in the body; severally modifying each other, though under conditions scarcely even surmised in our present knowledge.

Not less worthy of notice are those curiously anomalous cases, which occur in conjunction with scarlatina, when this disease is prevailing alone. In close contact with distinct and violent instances of the disorder, we find others in which the influence of the same virus is manifestly present, but where the symptoms are incompletely evolved; often so partially, as to wear every appearance of other and different disorders, and frequently to obtain wholly different names; yet, amidst all these anomalies, capable by diligent observation of being referred to a common cause. I shall have occasion to speak again on this curious subject of the incomplete development of disease from a virus of given kind, insufficiently received for complete effect, or acting on peculiar temperaments of body.

showed the ambiguous symptoms described above, and another child passed from the influenza into a fever, having the typhoid or adynamic type.

I add a further note here regarding the latest of these epidemics, that of the early part of 1838. Scarlatina was again very prevalent in London at the same time; and I noticed several of the anomalous cases cited above, though less remarkable than those of former years; possibly because the influenza itself was less severe in degree. Sir G. Baker notices the tendency to angina and erratic efflorescence of the skin in the remarkable influenza of 1762.