PARASITIC DISEASES OF THE HORSE 161 



PARASITES DERIVED FROM THE PLANT WORLD 



Classification. Parasitic plants belong for the most part to the large 

 family of fungi. Their history is in many points obscure, and the various 

 attempts at classification have not been entirely satisfactory. For the 

 present purpose, however, it will be sufficient to refer to three divisions: 

 schizomycetes, saccharomycetes, and actinomycetes. The schizomycetes 

 include the fungi which multiply by division or fission, the saccharomycetes 

 or yeast fungi multiply by budding and the formation of spore, actinomy- 

 cetes include the fungi the branches of which radiate from a centre-rayed 

 fungus. Individuals of the two first divisions are found on the surface of 

 the body and in the internal organs of the horse, but so far as is known 

 very few of them produce disease. 



PARASITES DERIVED FROM THE ANIMAL KINGDOM 



Classification. Animal parasites are divided into three classes: 

 1. Protozoa. 2. Helminths. 3. Arthropedes. 



Protozoa include all organisms of the most simple form the mere 

 beginnings of life, in reality' from the small structureless mass of living 

 material (bioplasm) to the different forms of cells consisting of a simple 

 investing membrane containing nuclei or sometimes only granular material. 

 Cells assume various forms circular, oval, elliptical, and elongated. 



Protozoa include amoebae, sporozoa, and infusoria. Amoebae have no 

 defined outline, but consist of small masses of living material capable of 

 moving in any direction, and feeding upon particles of food which they 

 find in the fluid in which they live. Those particles they appropriate by 

 enclosing them in the jelly-like material of which they are composed. 



Sporozoa are divided into gregarines, coccidia, and psorosperms. They 

 have a more definite form than amoebae, as they are bounded by a 

 cell-wall and contain spores or nuclei. All of these primitive forms of 

 life inhabit stagnant pools, and are consequently taken in by animals 

 which are feeding on the pastures. Their presence has frequently been 

 recognized in the digestive organs of animals, but it is only of late years 

 that the truly parasitic character which some of them assume has been 

 realized. Fatal outbreaks of disease among pheasants and poultry have 

 been traced to the invasion of coccidia, and the presence of the same 

 organism in the ducts of the liver of the rabbit has probably been respon- 

 sible for a considerable mortality among those animals. The true signifi- 

 cance of these lowest forms of parasitic life in the organs of warm-blooded 

 animals is not yet fully appreciated. 



f VOL. II. 46 



