PARASITIC DISEASES. An important subdivision in the classification of disease. (See NosoLocr.) In these diseases certain morbid conditions are induced by the presence and vital activities of various low forms of animal or vegetable life, which have found lodgment and subsistence in some ti--ue or organ. or upon some surface of the body of man or animals. Even plant, are not exempt from disorders of this na ture. See PARASITE. PLANT.
The vegetable microorganisms which cause dis ease are far more numerous and important than the animal. but are as yet less perfectly under stood. They may be divided into three classes: 11) the Mastonayectes or yeast fungi: (2) the Ny1,holtlyret[.S, or mold,; and (3) the 8chizorny cetcs or bacteria.
(1) The yeasts are important only as causes of fermentation. One member of the family. however, is pathogenic. and grows upon the mu cous membrane of the mouth and throat. This is the Oidiurn albicaus. and the disease it gives rise to is called thrush (q.v.). Yeasts are common in the stomach, being introduced with the food. and are found in diabetic urine.
(2) The pathogenic mold, are found upon the surface of the body. sinee they require free oxygen for their growth. They are responsible for many skin disease,. Favu, (q.v.) is caused by the Anchorion Sehonleinii. l'ityriasis rersi color. also called chloasma. is caused by the Miserosporon furfur. Actinonlycosis (q.v.) is due to infection by the ray fungus I aetino myces). Madura foot is a serious disease.
ring in the feet of native- of India. and was shown in 1861 by Carter to be due to a fuivm,— eh ion yphe rt eri.
(3) The Schizomycetes or bacteria are by far the most important and interesting of the vege table parasites. They penetrate every tissue of the body and are lalOWD to be the cause of most of the specific febrile diseases. and are suspected to be the cause of others, The study of these organisms has almost reached the dignity of a separate science. See BACTERIA.