416 VETEEINAEY HYGIENE 



security ; but it may at once be said, and the fact will be 

 very apparent in the following pages, that sheep with 

 fluke, cattle with stomach, and horses with intestinal 

 strongles, are a greater risk of infection on pasture lands 

 than if the animals were suffering from anthrax. The 

 anthrax animal is only dangerous if its blood be shed, but 

 every evacuation from the above parasitic patients may be 

 a source of future trouble, and, in the same way, every 

 cough from the calf or sheep with ' husk,' scatters the ova 

 of the parasite broadcast. 



When it is remembered that a pure water-supply and 

 clean pastures would practically eradicate many of the 

 internal parasitic diseases, it is obvious that the remedy 

 lies in the hands of the owner. We deprecate grand- 

 motherly legislation, but it is not too much to ask that 

 owners of animals should be compelled to provide a pure 

 source of water, clean surroundings, and suitable protection 

 for animals, and this is the only class of legislation against 

 disease, viz., prevention, which should be delegated to the 

 local authorities. 



Parasites are organisms which pass the whole or part of 

 their life living on and being nourished by other organisms. 

 They may belong to the vegetable or animal kingdom, and 

 in these attacks a distinction is made between those that 

 only by accident, as it were, live on animals, and those 

 which are unable to live or complete their cycle of existence 

 in any other way. The former are called facultative or 

 occasional, the latter obligatory or constant parasites. 



Animal parasites may be divided into two classes, those 

 that live outside and those that live within the body. 

 Zoologically, they are divided into three groups, the arthro- 

 podes, worms, and protozoa. The latter will be considered 

 in the chapter dealing with bacteria. 



We cannot within the scope of this work do more than 

 draw attention to the various parasites, excepting those 

 which are pests or cause widespread disease, and these will 

 be dealt with in greater detail. 



Aethropodbs.— The Acarina consists of several families, 



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