Thus, physicians, much exposed to its influences in the discharge of their professional duties, are known to be relatively exempt, while other individuals, few in number it must be admitted, have either had repeated attacks of the malady itself, or, after each exposure to its contagious principle, a recurrent illness of variable type. In the immense majority of all cases, however, one attack confers immunity upon the sufferer against subsequent invasion of the disease for the remainder of life. Upon a few occasions I have known variola to occur in individuals previously affected with cutaneous diseases, especially the eczematous—a fact which merely suggests that such pre-existing disorder of the integument conferred no immunity against infection.
SYMPTOMATOLOGY.—The earliest symptoms of small-pox may be occasionally recognized during the stage of incubation, which, as described above, embraces a period of from ten to fifteen days, though these limits are not absolutely fixed, since both shorter and longer incubative periods have been at times established. During the interval the patient may appear to enjoy perfect health, or, on the other hand, suffer from an ill-defined malaise, with anorexia, languor, insomnia, and allied symptoms. Close observation of the patient thus affected will often reveal the existence of a peculiar pallor of the face, accompanied by a skin-color which suggests a slight degree of sallowness of the complexion. These rather indeterminate symptoms are naturally most marked toward the completion of the period of incubation.
The latter terminated, the period of invasion follows, and extends from the conclusion of the incubative stage to the moment when the first cutaneous lesions of variola appear upon the surface. The symptoms which characterize the onset of this period of invasion are conspicuous and characteristic. There is often a sharp vespertine rigor or a more or less continuous chilliness, accompanied by sensations of "creeping" over the surface, lasting even for several hours. Meantime, the temperature rises to 103° or 105° F., the pulse running up to 120 or 130 beats per minute. In this febrile condition there is commonly complaint of a characteristic aching in the head and back, intense, scarcely intermittent, and so peculiar as to have frequently furnished a clue to the diagnosis of the approaching malady. These sensations are quite analogous to the substernal and other pains which frequently precede the first explosions of syphilis, and are all, without question, due to the circulation of a poisoned blood, the influence of which is in this manner confessed by the nervous system. In the case of infants and young children the invasion of small-pox is frequently ushered in by delirium and convulsions—symptoms which are to be explained by the facts just named.
This complexus of febrile and nervous symptoms, varying somewhat in intensity and possibly interrupted by sensations of chilliness, may be recognized as continuing on the second and third days of the period of invasion. Meantime, there may be noted a dusky hyperæmia of the pharynx and tonsils, the surface of which may even display elevated points which develop later into papules. In exceptional instances the intensity of the poison is such that the system fails to rally before the violence of the onset, and a fatal result ensues before the characteristic exanthem appears upon the skin.
On the second and third days of the invasion stage of the disease, if they are displayed at all, the variolous rashes appear. Too much attention can scarcely be paid to the importance of their recognition on the part of the diagnostician. Often indeed have practitioners been deceived by their occurrence, having been either completely blinded to the serious nature of the malady in progress, or, as Bartholow2 has well shown, having supposed that they were dealing with a concurrence of variola and scarlatina or rubeola.
2 "The Variolous Diseases," Med. News, Mar. 4, 1882, p. 232.
Hebra was the first to point out the significance of the rash known as roseola variolosa or erythema variolosa. Occurring at about the dates named above, it is in a few patients pronounced and vivid, even in solitary instances rivalling in severity the exanthem which succeeds it. In others, the majority of all patients in some epidemics, it may be entirely wanting. The writer has certainly observed its most typical development in women who were either menstruating or in the puerperal state. It is said also to be relatively frequent in subjects of a tender age. Kaposi3 has recognized it in all its manifestations at every age.
3 Consult the admirable chapter on variola in his treatise, Path. u. Therap. der Hautkrankt, Wien, 1882.
It appears in the form of puncta, striæ, or diffuse and uniform blushes covering extensive areas of the integument, livid red, purplish, or brownish-red in hue, paling under pressure, but never leaving upon the skin over which the finger-nail is quickly drawn the characteristic whitish streak by which many practitioners test the scarlatinal rash. The surfaces involved may be either not raised or slightly elevated above the general level of the skin, and are usually circumscribed. The regions chiefly involved have been carefully described by Th. Simon, and are hence sometimes called Simon's triangles. Thus the groin, the internal face of the thighs, and the hypogastric region may be involved at once (femoral triangle of Simon); the surface of the axilla, the pectoral region, and the inner face of the arm (brachial triangle of Simon), as also the extensor faces of the knees and the elbows, the dorsum of the feet, and indeed every portion of the surface of the body.
In the midst of these rash-covered areas may also appear petechial or hemorrhagic, dark-red, pin-head to bean-sized maculæ, which undergo color-changes both in lighter and deeper shades as the invasion period lapses. In lieu of these, however, transient wheals may come and go over the surface, and even the erythema described above may assume an erratic phase and appear in one part only to disappear and recur at another. None of these flash-light warnings of the oncoming exanthem are proportioned to the latter in the matter of extent and intensity of development. They may be followed by grave or mild manifestations of the disease. The subsequent eruption may also be much more abundantly developed in regions where the invasion rashes have not appeared, and the latter completely fade before the former have advanced to occupy the field thus deserted.