A disease which in many respects is allied to croup, but which differs from that affection in that it is of contagious character. It is attended with fever, which usually appears to arise from cold and sore throat, but which ends in a specific affection of the throat. In bad cases the windpipe and air-passages become cov ered with a tough membranous exudation, which may separate like a piece of leather from the mucous surface. Diphtheria is most frequent and fatal in children, but it attacks persons of adolescent and middle life, and it is extremely fatal. There are some persons who seem more susceptible than others to its influ ence, and there can be no doubt that the tendency to it runs in particular families. Although manifesting itself by the most marked local signs in the throat, it is a general disease in which there is a tendency to separation and coagulation of the fibrinous part of the blood. It is often rendered rapidly fatal by the sepa ration and coagulation of the fibrine of the blood within the heart.
The period of incubation, according to my observation, is from three to six days. The crisis is about the fifth day.
Diphtheritic Paralysis. Diphtheria is sometimes followed by paralysis of some of the muscles of the body. The palsy affects mostly the muscles used in swallowing, but it sometimes extends to the muscles of the neck, and even to those of the limbs. I have seen it once extend so as to include the whole of the mus cles of the right side of the body. It is, I believe, due to a pro cess of coagulation iu the nervous fibres. As a rule persons of fair general health recover from it under conditions favorable for recovery.