THE DOG AS A CAKEIER OF PAEASITES AND DISEASE. 17 



do the dozens of other dangerous and improper things that some dogs 

 are allowed to do. 



The presence of one or a few of these tapeworms in man probably 

 occasions very little inconvenience as a rule. At the same time the 

 tapeworm has an unpleasant habit of burrowing through the intesti- 

 nal mucosa, thereby destroying its integrity and exposing it to the 

 attack of any pathogenic germs that may be present in the intestine. 

 The same burrowing habit makes it difficult to remove successfully 

 the entire worm with the head, and a failure to remove the head, 

 owing to its being buried in the mucous lining of the intestine, results 

 in the subsequent development of new tapeworm segments from the 

 head and a renewal of infection. At its best, a tapeworm is a thing 

 unpleasant to contemplate as an inhabitant of our intestines. The 

 presence of the tapeworm under discussion here is, moreover, 

 evidence of careless or unclean habits on the part of the person 

 infested. 



Prevention requires that the unwarranted liberties and freedom of 

 the dog be curtailed ; that he be kept free not only from tapeworm 

 but from such external parasites as fleas and lice. The accomplish- 

 ment of the latter measure calls for keeping a dog clean and restrain- 

 ing him so that he will not be allowed to run at large with vagrant 

 flea-infested and lousy dogs. 



Roundworm. — Among the other parasites of the dog there is a 

 -nematode or roundworm, scientifically known as Toxascaris linibata^ 

 which, like the tapeworm just mentioned, may occur in man in the 

 same form in which it occurs in the dog. This worm does not have 

 an intermediate stage in another animal, but is conveyed directly 

 through the eggs produced by the female worm, which eggs normally 

 convey the infection from a dog back to the same or another dog, 

 either in contaminated food or water or as the result of the con- 

 tamination of the skin and the subsequent cleansing of the skin by 

 means of the tongue. 



Under the conditions of unwarranted association and familiarity 

 with dogs already mentioned, eggs of this parasite and of an allied 

 parasite in the cat may be ingested by man, and especially by chil- 

 dren, and subsequently develop into the adult worm in the intestine. 

 These worms may produce unpleasant results. The entire group of 

 ascarids are notorious for their wandering habits. They not in- 

 frequently travel to the stomach and produce vomiting, in the course 

 of which the worms may be brought up. It is hardly necessary to 

 say that the vomiting of worms 4 or 5 inches long is a distinctly 

 unpleasant experience, and this is one of the least unpleasant results 



