Introduction to the Study of Disease 



detect them, it is necessary to resort to micro- 

 scopic examination, for which professional aid is 

 required. They are known as flagellated 

 infusoria, and many other diseases in tropical 

 countries arise from a similar cause. Internal 

 parasites, such as worms, are known as entozoa, 

 in contra-distinction to animal parasites residing 

 on the outside of the body and which are termed 

 epizoa. Round and flat worms afford a good 

 example of the former class, and mange mites of 

 the latter. 



The detrimental influences of the entozoa is 

 due to their mode of life, their nourishment being 

 directly derived from their host, and in some cases 

 their destructive effects upon the living tissues. 

 Epizoa, on the other hand, excite congestion of 

 the skin and live upon, and multiply within the 

 products of the inflamed area. Ringworm is a 

 very common disease in calves and results from 

 invasion of the hair and hair follicles by a 

 vegetable fungus belonging to a class of parasites 

 known as Protophyta, which are allied to the 

 yeast plant. Diseases, such as Anthrax, Tuber- 

 culosis, Glanders, Swine Fever, Distemper, 

 Strangles, Influenza, etc., are due to a class of 

 microscopic organisms known as Bacteria, Bacilli, 

 Micro-cocci, etc., all of which are capable of 

 marvellous powers of multiplication, requiring 

 high powers of the microscope for their demon- 

 stration, along with suitable staining re^-agents, 



xxxi 



