Yaws : its nature and treatment an introduction to the study of the disease / by J. Numa Rat.
- Rat, Joseph Numa.
- Date:
- 1891
Licence: Public Domain Mark
Credit: Yaws : its nature and treatment an introduction to the study of the disease / by J. Numa Rat. Source: Wellcome Collection.
19/74 (page 7)
![derma, protrude through the epidermis, discharge a non-purulent, acid fluid, and usually dis¬ appear by interstitial absorption in from three to twelve months. Under unfavourable circum¬ stances, the neoplastic growth infiltrates the surrounding tissues both superficial and subcutaneous, undergoes necrosis, and excites destructive inflammation of the deepest tissues, occasionally involving even the bones. Stages.—The clinical history of the affection suggests a division into four stages which may be described as follows:— (1.) The Incubation Stage.—Between the moment of the reception of the virus and the development of the initial lesion at the seat of contagion. (2.) The Primary Stage.—Between the appearance of the local, initial lesion and that of the general, superficial, eruption. (3.) The Secondary Stage.—Between the commencement and termination of the general superficial eruption. (4.), The Tertiary Stage.—That of deep seated lesions, such as exedent ulcers, periostitis, gummata, &o. Incubation Stage. In determining the duration of this stage, observers have generally taken the time elapsing between the moment of inoculation or contagion and the first manifestation of the skin lesion, whether local or general; but it is evident that, as the local lesion (at the point of contagion) normally precedes the general eruption by a considerable interval, the appearance of the former should be taken to represent the termination of the incubation period. Any attempt to estimate the term of incubation of a disease by clinical observation of ordinary cases is so obviously liable to error that dependence, in this matter, should rather be placed on the teachings of inoculation experiments which are themselves, however, not entirely free from a similar objection. In places in which Yaws is endemic, apart from the possibility of inheritance, it is difficult to decide whether the person inoculated had not been previously infected, or, again, whether the disease has been caused by the virus experimentally introduced, or by subsequent accidental contagion through the wound of inoculation. To be exact, therefore, such experiments must be performed under circumstances which are so seldom obtainable, that it is only by observing the results of a very large number of them that any approximately reliable conclusion can be arrived at. A sufficient number of such experiments has not yet been recorded ; but from those that have been made it may be deduced that the incubation of the Yaws virus averages from three to ten weeks, the former being the most usual duration of that period. Cases have been recorded in which a shorter or longer interval has elapsed between the supposed moment of infection and the earliest cutaneous manifestation of the disease ; but, allowing the probability of such exceptional instances, there are possible errors, in connection with these observations, in addition to. those already cited, which should not be disregarded. The course of every disease is subject to modifications due to causes acting directly or indirectly on the system; and among these may be mentioned the health of the patient, the subjection of the mind or body to unusual or unusually prolonged influences, the supervention of another disease, &c. In the case reported by Thomson, of yaws following variolous inoculation after an interval of two months, the variola appearing first, the development of the more chronic was doubtless retarded by the presence of the more acute and more active affection. There are other circumstances which must, also, be taken into consideration in estimating the length of the incubation period, viz. : the age, nationality and physical condition of the supplier of the virus and of the recipient of it; and, with regard to the virus itself, its amount, its direct source, and its age, on which two latter circumstances its activity depends. With respect to the nature of the tissue inoculated or infected, it is plain that the rapidity with which the virus is absorbed must depend on the permeability of the seat of contagion, such conditions as extensive excoriations and large ulcers, &c., affording special facilities. When a concomitant affection has modified the course of the disease, there is the probability also of a corresponding influence having been exerted on the Yaws virus which has altered its activity. We know, too, that the.virulence of epidemics varies with times and circumstances, and that infectious diseases attack virgin communities with exceptional violence. Similar conditions may, therefore, operate to alter the nature of the virus of an affection like Yaws, and results obtained in places where the disease has.been newly or comparatively newly introduced may, for that reason, differ from those observed in others in which it has been long endemic. Some of the circumstances already mentioned would explain differences in the incubation period in the same locality : and such differences would again depend on that important factor, individual susceptibility. There are no special symptoms to be recorded in connection with the incubation stage. Being unaware of the changes taking place in his system, the patient takes no note of any derangement.of his health which may occur during this period, or, should he do so, attributes them to an incipient catarrh, or malarial fever, or to disordered digestion. While the little attention paid to suoh deviations from health makes it most probable that the subjective symptoms, in cases of ordinary infection, can only be trifling, it is impossible to suppose that a disease which is capable of affecting the system so profoundly can occupy it for several weeks without inducing considerable changes in one or more of its tissues. In cases of inoculation which have come under my notice, the following, symptoms were observed. The skin is dry ; its papillae are unusually prominent; there is a loss of pigment in certain portions of the skin at different parts of the body, but chiefly in the neighbourhood of the site of inoculation, producing light coloured [174674] 50 5](https://iiif.wellcomecollection.org/image/b30556752_0019.jp2/full/800%2C/0/default.jpg)
