Fig. 243.—Tænia saginata. 19, egg with external shell. 20, without (embryophore). (After Leuckart.)
T. saginata in its adult condition lives exclusively in the intestinal canal of man.[291] The corresponding cysticercus is Cysticercus bovis, and is found almost exclusively in the ox; it is small, 7·5 to 9 mm. in length and 5·5 mm. in breadth, may easily escape notice, and requires from three to six months for its development. Numerous experiments have confirmed the connection of Cysticercus bovis with Tænia saginata; indeed, the cysticercus was only discovered by feeding experiments after attention had been called to the ox as the probable intermediary host of this Tænia.
Fig. 244.—A piece of the muscle of the ox, with three specimens of Cysticercus bovis. Natural size. (After Ostertag.)
Medical men observed that weakly children who were ordered to eat raw scraped beef to strengthen them contracted T. saginata. It was found, moreover, that Jews, who are prohibited from eating pork from religious motives, suffered especially from T. saginata; when T. solium was found to occur in a Jew he often confessed to having eaten pork; and finally it was found that certain nations—for instance, the Abyssinians—frequently harbour T. saginata, and only eat beef—raw by preference.
These observations led Leuckart, in 1861, to feed young calves with the proglottids of T. saginata in order to discover the corresponding cysticercus, which was then not known. This experiment was successful. Similar experiments, with similar results, were then conducted by Mosler (1863), Cobbold and Simonds (1864 and 1872), Röll (1865), Gerlach (1870), Zürn (1872), Saint Cyr, Jolicœur (1873), Masse and Pourquier (1876), and Perroncito, in 1876. The attempts to infect goats, sheep, dogs, pigs, rabbits and monkeys were unsuccessful. Only Zenker and Heller were able to infect kids, and Heller infected one sheep, but these are exceptions.
Artificial infections of human beings with Cysticercus bovis to obtain the tapeworm were less numerous, and indeed quite superfluous, yet this was also done by Oliver (1869) in India, and Perroncito (1877) in Italy. The experiments of the latter prove that the extracted cysticerci of the ox certainly perish in water at 47° to 48° C.