Fig. 238.—Tænia solium. 21, Egg with external membrane; 22, without (embryophore). (After Leuckart.)
Even with the naked eye a white spot may be observed in the centre of the long equator, this being the invaginated head; it is easy to make it project by pressing on the vesicle (after tearing off with the finger-nail the investing connective tissue), and on examining it under the microscope one can convince oneself that it corresponds with the head of Tænia solium.
Fig. 239.—Two mature proglottids of Tænia solium with fully developed uterus. 2/1.
Numerous experiments have proved that the Cysticercus cellulosæ of the pig, if introduced into the intestine of man, grows to a Tænia solium (Küchenmeister, 1855; Humbert, 1856; Leuckart, 1856; Hollenbach, 1859; Heller, 1876); the cysticercus has frequently also been cultivated purposely by feeding pigs with mature proglottids of T. solium (P. J. van Beneden, 1853; Haubner and Küchenmeister, 1855; Leuckart, 1856; Mosler, 1865; Gerlach, 1870; etc.), but success did not attend the efforts to make Cysticercus cellulosæ establish themselves in the intestines of pigs, dogs, guinea-pigs, rabbits and monkeys (Macacus cynomolgus), and so become adult Tæniæ; the attempts, also, to infect dogs with cysticerci by means of ova were likewise, as a rule, abortive.[288]
The development of Cysticercus cellulosæ takes two and a half to three or four months; it is not known how long the cysticerci remain alive in animals; not uncommonly they perish at earlier or later stages, and become calcified or caseated. Extracted cysticerci die in water at a temperature of 47° to 48° C., in flesh at normal temperature they remain alive for twenty-nine days or more. On account of the present rapid means of pickling and smoking meat, the cysticerci as a rule are not killed, also the effect of cold on them for some time in cold chambers of slaughterhouses is not lethal, but freezing is fatal (Ostertag).