354 



THE ANIMAL PARASITES OF MAN 



investigations of Kobert, Joest, etc., have, however, shown the harmlessness of fresh 

 undecomposed hydatid and cysticercus fluid for rabbits, mice and guinea-pigs, whether 

 inoculated intraperitoneally, subcutaneously or intravenously. Contrary data or 

 clinical experience must accordingly depend on other factors. 



According to the researches of Leuckart, the growth of the 

 echinococcus is very slow ; four weeks after infection the average 

 size is only 0-25 to 0-35 mm., at the age of eight weeks it is i to 

 2-5 mm., and at this period the formation of the central cavity com- 

 mences ; at the age of five months, and with a size of 15 to 20 mm., 

 the first brood capsules with scolices are formed. The conse- 

 quence of this gradual increase of size is that the organ attacked 

 can maintain its functions by vicarious hypertrophy, and that many 

 echinococci induce no special symptoms and cannot even be 

 diagnosed, the latter circumstance being due to their hidden position. 



The echinococcus cannot be said to be scarce in man, as is 

 shown by the following table for Central Europe : 



These, however, are only cases that have become known by post- 

 mortem ; in addition, there are cases that have been treated medically, 

 of which there are a few statements, at all events relating to the 

 principal districts of Germany. According to Madelung, one case 

 of echinococcus occurs in every 1,056 inhabitants in the town of 

 Rostock, in the district of Rostock one to every 1,283, in Schwerin 

 one to every 5,887, and in Ludwigsort one to every 23,685 ; according 

 to Peiper, in Upper Pomerania one case occurs to every 3,336, 

 in the district of Greifswald one to every 1,535 inhabitants. The 

 northern districts of Pomerania are more affected than the southern 

 ones. 



Accordingly, echinococcus is also considerably more frequent in cattle in 

 Pomerania. On an average in Germany 10-39 per cent, oxen, 9*83 per cent, sheep, 

 and 6' 47 per cent, pigs are infected, whereas in Upper Pomerania 3773 per cent. 



