PROTOZOA 253 



The Protozoa are unicellular bodies which can only live 

 in a moist or liquid medium, and in the absence of moist 

 nutrient material they become converted into round re- 

 sistant cysts. Protozoa may also possess a kind of larval 

 condition, consisting of small roundish or irregular masses 

 of protoplasm which move by means of projecting, limb- 

 like processes (pseudopodia), or in some cases by flagella. 

 They frequently lose their motility when they take up their 

 residence in other cells. The contents of the cysts separate 

 by division into particles known as sporocysts, the contents 

 of which break up into a number of sickle or crescent like 

 bodies. 



The various divisions of the Protozoa are known as Plas- 

 modia, Coccidia, Psorospernii, Amoeba, etc. 



The parasite occurring in the blood in malaria, known 

 as the Plasmodium malarice, has already been described 

 (see p. 221 et seq.). 



Protozoa have been described by many observers as 

 occurring in dysentery, carcinoma, sarcoma, in a form of 

 ' eczema ' of the nipple known as Paget's disease ; also in 

 other pathological and morbid conditions of the human and 

 animal subject. 



A very fatal disease in young rabbits, due to a parasite 

 known as the Coccidium oviforme, has recently been 

 thoroughly studied by Pfeiffer, although its existence was 

 known as far back as 1839. In India a fatal disease 

 known as surra occurs in horses, mules, camels, etc. 

 The cause of the disease, which is characterised by fever, 

 jaundice, and great prostration, followed by death, is 

 ascribed to the presence of a flagellated parasite which 

 occurs iu the blood of the affected animal in vast numbers. 



Surgeon-Major Bruce, of Natal, has recently investi- 

 gated the fatal disease which occurs in horses, etc., 

 caused by the bite of the tsetse fly. Dr. Bruce finds 



