The illness varies within the widest limits, and exhibits all gradations of severity, from a mere indisposition, which may pass almost unnoticed, to an extreme violence, only equalled by the most violent forms of cholera. The mild cases are always bubonic ; the other varieties are invariably severe, and almost always fatal. Incubation is generally from f our to six days, but it has been observed as short as thirty-six hours and as long as ten days (Bombay Research Committee). As a rule the onset is sudden and well marked.
(I) Bubonic cases usually constitute three-fourths of the whole, and the symptoms may therefore be called typical. In a well-marked case there is usually an initial rigor—in children convulsions—followed by a rise of temperature, with vomiting, headache, giddiness, intolerance to light ; pain in epigastrium, back and limbs; sleeplessness, apathy or delirium. The headache is described as splitting; delirium is of the busy type, like delirium tremens. The temperature varies greatly ; it is not usually high on the first day—from 'or° to 103°—and may even be normal, but sometimes it rises rapidly to 104° or 105° or even 107° F; a fall of two or three degrees on the second or third day has fre quently been observed. The eyes are red and inflamed; the tongue is somewhat swollen, and at first covered with a thin white fur, except at the tip and edges, but later it is dry, and the fur yellow or brownish. Prostration is marked. Constipation is the rule at first, but diarrhoea may be present, and is a bad sign. A char acteristic symptom in severe cases is that the patient appears dazed and stupid, is thick in speech, and staggers. The condition has often been mistaken for intoxication. There is nothing, how ever, in all these symptoms positively distinctive of plague, unless it is already prevalent. The really pathognomonic sign is the appearance of buboes or inflamed glands, which happens early in the illness, usually on the second day ; sometimes they are present from the outset, sometimes they cannot be detected before the third day, or even later. The commonest seat is the groin, and next to that the axilla; the cervical, submaxillary and femoral glands are less frequently affected. Sometimes the buboes are
multiple and on both sides, but more commonly they are unilat eral. The pain is described as lancinating. If left, they usually suppurate and open outwards by sloughing of the skin, but they may subside spontaneously, or remain hard and indurated. Petechiae occur over buboes or on the abdomen, but they are not very common, except in fatal cases, when they appear shortly before death. Boils and carbuncles are rare.
(2) Pneumonic plague was observed and described in many of the old epidemics, but its precise significance was first recognized by Childe in Bombay. He demonstrated the presence of the bacilli in the sputa, and showed that the inflammation in the lungs was set up by primary plague infection. The pneumonia is usually lobular, the onset marked by rigors, with difficult and hurried breathing, cough and expectoration. The prostration is great and the course of the illness rapid. The breathing becomes very hurried—forty to sixty respirations in the minute—and the face dusky. The expectoration soon becomes watery and profuse, with little whitish specks, which contain great quantities of bacilli. The temperature is high and irregular. The physical signs are those of bronchopneumonia ; oedema of the lungs soon super venes, and death occurs in three or four days.
(3) In septicaemic cases the symptoms are those of the bu bonic type, but more severe and without buboes. Prostration and cerebral symptoms are particularly marked ; the temperature rises rapidly and very high. The patient may die comatose within twenty-four hours, but more commonly death occurs on the sec ond or third day. Recovery is very rare.
The case mortality of plague still remains exceedingly high. The lowest recorded is 34% in Sydney, and the highest 95% at Hong Kong in 1899. During the first few weeks in Bombay it was calculated by Dr. Viegas to be as high as 99%. It is very much higher among Orientals than among Europeans. In the Bombay hospitals it was about 7o% among the former, and be tween 3o% and 4o% among the latter, which was much the same as in Oporto, Sydney and Cape Town. It appears, therefore, that plague is less fatal to Europeans than cholera. The average duration of fatal cases is five or six days; in the House of Correc tion at Byculla, where the exact period could be well observed, it was five and a half days. Patients who survive the tenth or twelfth day have a good chance of recovery. Convalescence is usually prolonged. Second attacks are rare, but not unknown.