530 THE ANIMAL PARASITES OF MAN 



But how does the dog become infected ? Every one who has made observa- 

 tions in the rural districts knows perfectly well. The butchers as well as the 

 shepherds — the latter, as a rule, performing the duty of slaughter in the coun- 

 try — are familiar with the danger of the echinococcus. Any one who has been 

 in a farming country at slaughter time knows that the parts of the meat which 

 are unsuitable for human food, among these frequently the liver and the lungs 

 which are permeated with echinococci, are used as food for the dogs. Where 

 there is careful management, organs of this kind are buried, but rarely so deep 

 that the dog who sniffs about cannot finally reach them. A vicious circle is 

 formed: the infected cattle, sheep and swine furnish the scolices to the dog; 

 the dog furnishes the ova of the tenia. 



If we observe the frequently intimate relation of children as well as adults 

 with dogs, and how the dog will lick the face and the hands, we can scarcely 

 doubt that in this way, as well as by kissing, infection can be conveyed. Dogs 

 of every species sniff at their own ani as well as at those of other dogs ; often 

 they carry around upon their noses collections of mature proglottides without 

 these being noticed on account of their diminutive size. Toys which small 

 children often lick, pieces of bread scattered about in different corners of the 

 nursery, may readily become contaminated by the mature eggs of the tenia. 

 The dogs probably discharge the mature proglottides with the feces. In the 

 feces of other dogs they are fond of sniffing around. Thus the dog's nose 

 becomes contaminated, and the transmission of the ova of the tenia may occur. 

 Frequently the dog's feces are discharged in the vicinity of pumps and wells. 

 The proglottides and their ova continue to live for a long time on account of 

 the moisture here constantly present, so that they reach the human stomach 

 with the drinking-water as a still germinating brood. The teniae may also be 

 readily distributed by means of vegetables that are eaten raw, such as lettuce, 

 cabbage, berries and fruits which grow upon the earth. The number of ways 

 in which an infected material, or the eggs of the tenia, finally reach the intes- 

 tinal tract of man is infinitely great, and it is unnecessary to presuppose an 

 intimate association of the infected individual with dogs. 



The number of children infected appears very small when we consider the 

 fact that at this period of life, in consequence of close association with dogs, 

 they are particularly endangered. This observation is confirmed by all statis- 

 tics. In the Pomeranian investigation, among 139 patients only 13 were under 

 fifteen years of age. The majority of infections occur between the twentieth 

 and fortieth years of life. Probably in consequence of the slow development 

 of the echinococcus in the human organism, the germs acquired in youth, as 

 a rule, produce definite symptoms only in later years. That the course may 

 be chronic is shown by my collection of cases. Among others, a midwife, aged 

 sixty, from her twenty-fifth year (therefore for thirty-five years) had period- 

 ically coughed up echinococci. A farmer, aged forty, mentioned as the prob- 

 able period of invasion the time from his ninth to his twelfth year, since 

 during this period he always slept in a bed with several dogs. He had suf- 

 fered since his thirty-fifth year with frequent and repeated attacks of irrita- 

 tive cough with expectoration that contained echinococcus cysts. 



It is difficult to find proof from the statistics of Mecklenburg and Pome- 



