152 THE EFFECTS OF PARASITES ON THEIR HOSTS. 



The correctness of this conclusion is indubitably established by 

 experience and by experiment. Other animals furnish us, then, with 

 the largest contingent of our parasitic guests, but they transmit them 

 in very different stages. The parasites which we derive from the 

 animals used in food are adult forms, like the common tape-worm 

 and Trichina. We receive them, however, in a larval state, the tape- 

 worm in the form of the bladder-worm, the Trichina in its encap- 

 suled form among the muscles. Both these common forms are most 

 commonly derived from the pig, while Tcenia saginata is derived from 

 the ox. On the other hand, our household animals mostly furnish us 

 with the eggs or embryos of their parasites, which then attain in us 

 their larval stage. Among the latter class of animals the dog is pre- 

 eminent as the chief bearer of parasites. From him we derive Pen- 

 tastomum denticulatum, Cysticercus tenuicollis, 1 and especially Echino- 

 coccus, which arise when the ripe eggs of his Pentastomum tcenioides, 

 Tcenia marginata, and Tcenia echinococcus respectively are in some 

 way or other smuggled into us. 



The manner of infection varies according to circumstances, and is 

 largely determined by chance. It would be useless toil to recount all 

 the conceivable possibilities, but a few must be noted. The eggs of 



p. c., Trichocephalus in 2'5 p. c. Gribbohm reports for Kiel (out of 1117 examinations), 

 Ascarit in 18 '3 p. c., Oxyuris in 23 '3 p. c., and Trichocephalus in 32*2 p. c. ; and 

 estimates the sum total of sufferers from parasites in all to be 43 '5 p. c. ; and after de- 

 ducting children under half-year, at 49 P 8 (in women, 53 '8 p. c., in children half a year to 

 15 years old 50 p. c., in men 467 p. c. ). The other parasites have only a small per- 

 centage in comparison to the round- worms. Out of 1117 cases Pentastomum denticulatum 

 was found in 12 ; Cysticercus cettulosce 6 times ; Echinococcus, 3 times ; Tcenia saginata, 

 twice ; Tcenia solium and Trichina each once. I add further that among the 3694 post 

 mortem sections reported by Muller there occurred 17 cases of Tcenia solium ; 5 of T. 

 saginata ; 36 of Cysticercus cellulose?, 9 of Echinococcus. (In Gottingen, Forster found, 

 among 639 bodies, 3 with Echinococcus, and 4 with Cysticercus.) According to Daconta 

 (Zeitschrift fur Epidemiologie, Th. i.) there is one tape-worm patient in Thiiringen for 

 every 3315 inhabitants ; in the medical districts of Eisenach, Apolda, Jena, and Weimar, 

 however, there is one for every 486. For the town of Hanover even 2 p. c. of tape-worm 

 patients have been computed. Cruse found in Dorpat Bothriocephalus latus, at 482 post 

 mortem dissections, in 6 p. c. (Dor-pater med. Zeitung, Bd. ii., p. 315), Ascaris lumbricoides 

 in 9'9 p. c. In comparison with these statements, I remark that Krabbe saw in Copen- 

 hagen and the surrounding district, among 500 dogs, 336, that is 67 p. c., infected with 

 Helminths. Atcaris marginata was found in 24 p. c. ; Tcenia marginata in 14 p. c. ; T. 

 cucumerina in 48 p. c. The rest of the Helminths occurred much less often Tcenia 

 cosnurus in 1 p. c. ; T. serrata in 0'2 p. c. ; T. echinococcus in 0'4 p. c. ; Bothriocephalus 

 sp. in 0'2 p. c. ; Dochmius trigonocephalus in 2 p. c. (" Recherches helminthologiques, " 

 p. 3 : Copenhagen, 1866). It was different in Iceland, where Krabbe found, in 100 dogs, 

 Tcenia marginata 75 times ; T. ccenurus 18 times ; T. echinococcus 28 times ; the T. 

 cucumerina 57 times ; T. lagopodis 21 times ; Bothriocephalus 5 times ; and Ascaris 

 marginata only twice. There were only 7 dogs free from parasites in Iceland. Ibid., 

 p. 21. 



1 Krabbe considers the occurrence of Cysticercus tcnuicottis in man as doubtful, 

 Ugeskrift fur Laeger, Bd. xxxvii., No. 5, 1862. 



