PARASITIC DISEASES. It has long been recognized that various specific pathological conditions are due to the presence and action of parasites (see PARASITISM) in the human body, and during the last 5o years the part played in the causation of the so-called infective diseases by various members of the schizo mycetes or fission fungi has been widely and thoroughly inves tigated. During the past 20 years many diseases have been ascribed to filter passing viruses. Below are given lists of the prin cipal morbid conditions ascribed to these two groups of causes: A.—Morbid conditions affecting man due to vegetable para sites: Suppuration, septicaemia, infective endocarditis, erysipelas, gonorrhoea, soft chancre, nasal catarrh, pneumonia, acute rheuma tism ( ?), cholera, typhoid fever, paratyphoid fevers, epidemic diarrhoea, bacillary dysentery, malta fever, plague, diphtheria, tetanus, anthrax, influenza ( ?), tuberculosis, glanders, leprosy, epidemic cerebrospinal meningitis, dental caries, tularaemia, actinomycosis and other streptothricoses, aspergillosis, favus and other skin diseases, whooping cough.
B.—Morbid conditions affecting man due to filter-passing viruses : yellow fever, rabies, vaccinia, variola, dengue, sandfly fever, trachoma, poliomyelitis, measles ( ?), typhus fever, trench fever, mumps (?), herpes labialis, influenza (?), common colds.
Discussion of the general relation of vegetable parasites to disease is contained in articles on BACTERIA; IMMUNITY; VAC CINE THERAPY; and of filter-passing viruses in FILTER-PASSING VIRUSES. In this article the part played by protozoal and other animal causes of disease is considered.