MALIGNANT DISEASES, a name applied to those affections of the animal system characterized by a disposition to the formation of products which have the power of propagation at the expense of the normal tissues, or which so poison the blood that it soon becomes unfit to maintain life. Some of these diseases are tumors (q.v.), and come within the province of the surgeon, while others are the subjects of the physician. The principal malignant tumors are cancer (q.v.), and sarcoma (q.v.). The term malig nant applied to diseases not surgical is sometimes rather indefinite, although in some cases the application is entirely appropriate. Scarlet fever, when of a very severe form, with sloughing of the affected tissues of the throat, and with blood-poisoning to the extent of producing death in 48 hours, is truly.called malignant; but when less severe, although very dangerous, it is often called semi-malignant, and most cases are character ized by more or less tendency to malignancy. So in diphtheria, the severe cases, and
which are more properly called putrid fever, or malignant sore throat, are essentially malignant. Asiatic cholera (q.v) is a malignant disease, and one of its names is malig• nant cholera. Malbmant pustule (q.v) is also a malignant affection, but according to John Hunter's definition it would, perhaps, come under the head of tumor. One form of intermittent fever (q.v.) is truly malignant, as in some cases it is incurable, poisoning the blood and affecting the nervous system in a really malignant rnanner. There are forms of small-pox which are called malignant, but the term in this disease is of rather indefinite application, the disease not being essentiallv malignant, and only taking on that character because of the excessive amount of morbid matter, whereas the poison of diphtheria and of malignant or pernicious intermittent fever appears to pos sess intrinsic malignancy independent of quantity.