170 THE EFFECTS OF PARASITES ON THEIE HOSTS. 



more thorough-going measures must be taken in regard to water- 

 supply, dung-hills, and drains, as well as in regard to slaughter-houses 

 and the treatment of the flesh. What has already been provided 

 for by sanitary regulations is by no means sufficient nor in keeping 

 with the progress of science. We shall refer only to the regulations 

 about measly flesh, which in many places allow it to be sold raw, if 

 the bladder- worms are " not numerous," though never in the form of 

 sausage or similar preparations, though it is just this last process which 

 renders the cystic worms somewhat harmless. The measures taken 

 against Trichina also admit of manifold improvement. It is above 

 all necessary to popularise the facts known about parasites and their 

 origin, and even to make this a subject of instruction in schools. 



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