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by this process. Notwithstanding this, there are a few diseases 

 belonging to these two groups that do not require the agency of an 

 intermediate host, such as insects or acari, but are communicated 

 by direct contagion or contact. The most notable instance of 

 this is the Syrian equine trypanosomiasis or dourine, which is 

 transmitted by copulation or inoculation. The bubonic plague 

 of man, due to a special bacillus, is conveyed by the rat-flea. 



All those diseases that are due to a micro-organism or 

 microbe and can be transmitted to an animal, whether by direct 

 contact, inoculation, the agency of insects, or food and water, are 

 included under the generic term of infective diseases. 



A great deal of misconception is still prevelant not only in 

 the lay, but also in the professional mind, as to the hereditariness 

 of certain contagious or infective diseases. It is quite true an 

 animal or child may be born suffering from a contagious malady, 

 but this is no proof that the disease is heredity. Unless the 

 accidental germ be in the parent during utero-gestation no 

 disease will arise in the foetus. Even though the germ should 

 be in the parent, the offspring frequently escapes. 



To a disease appearing at birth the term congenital is given 

 in contradistinction to the term hereditary, which is now only 

 applied when the offspring develops some peculiarity, trait, or 

 disturbance that is handed down from ancestors and appearing 

 early or at some remote period after birth. 



The contagious diseases are due to micro-organisms or 

 microbes and parasites either belonging to the animal or vegetable 

 kingdoms. 



The micro-organisms are termed bacteria or protozoa, the 

 former belonging to the vegetable and the latter to the animal 

 kingdoms respectively. The science that deals with their natural 

 history is termed bacteriology or micro-biology. When the pro- 

 tozoa are alone studied the term protozoology is applied. 



The parasites are either vegetable or animal. To the latter 

 belong the parasitic worms, insects, and acari, that are conveyed 

 from one animalto another, either by direct or indirect means 

 and thus induce disease. The parasites belonging to the vege- 

 table kingdom are the moulds or fungi, which cause " ringworm" 

 —commonly termed in poultry " white-comb " — and the asper- 



