1. The malignant. It constitutes the highest grade of morbid diathesis. It is known by attacking frequently without a chilly fit, by coma, a depressed, slow, or intermitting pulse, and sometimes by the absence of pain, and with a natural temperature or coldness of the skin. It occurs in the plague, in the yellow fever, in the gout, in the small-pox and measles, in the hydrophobia, and after taking opium and other stimulating substances. Dr. Quier has described a pleurisy in Jamaica, in which some of those malignant symptoms took place. They are the effect of such a degree of impression as to prostrate the arterial system, and to produce a defect of action from an excess of force. Such is this excess of force, in some instances, in this state of fever, that it induces general convulsions, tetanus, and palsy, and sometimes extinguishes life in a few hours, by means of apoplexy or syncope. From its being accompanied with these symptoms, it has received the name of _adynamique_ by Dr. Alibert. The less violent degrees of stimulus in this state of fever produce palsy in the blood-vessels. It probably begins in the veins, and extends gradually to the arteries. It seems further to begin in the extremities of the arteries, and to extend by degrees to their origin in the heart. This is evident in the total absence of pulse which sometimes takes place in malignant fevers, four and twenty, and even eight and forty hours before death. But there are cases in which this palsy affects both the veins and arteries at the same time. It is probably from this simultaneous affection of the blood-vessels, that the arteries are found to be nearly full of blood after death from malignant fevers. The depressed, and intermitting pulse which occurs in the beginning of these fevers perhaps depends upon a tendency to palsy in the arteries, independently of an affection of the heart or brain. This _prostrate_ state of fever more frequently when left to itself terminates in petechiæ, buboes, carbuncles, abscesses, and mortifications, according as serum, lymph, or red blood is effused in the viscera or external parts of the body. These morbid appearances have been ascribed to putrefaction, and the fever has received, from its supposed presence, the name of putrid. The existence of putrefaction in the blood in a fever is rendered improbable, 1. By Dr. Seybert's experiments[5], which prove that it does not take place in the blood in a living state. It occurs in the excretions of bile, fæces, and urine, but in this case it does not act as a ferment, but a stimulus only upon the living body. [5] Inaugural dissertation, entitled, "An Attempt to disprove the Putrefaction of the Blood in Living Animals."