332 



THE ANIMAL PARASITES OF MAN 



Malformations are not so common as in T. saginata; they consist in two or 

 several proglottids being partly or entirely fused, formation of single club-shaped 

 segments, fenestration of long or short series of segments and so-called double forma- 

 tion, in which the head has six suckers and the segments exhibit a Y-shaped trans- 

 verse section. The oncospheres occasionally also possess more than six booklets. 

 Very slender specimens have led to the description of a particular species or variety 

 (T.tenella). 



In its fully developed condition T. soliutn is found exclusively 

 in man ; the head is usually attached in the anterior third of the 

 small intestine and the chain, in numerous convolutions, extends 

 backwards ; a few mature detached proglottids usually lie at the 

 most posterior part, and these are usually evacuated during defeca- 

 tion. In exceptional cases single proglottids or whole worms may 

 reach contiguous organs if abnormal communications with them 



FlG. 235. Two fairly mature proglottids 

 of Tcenia soliutn, showing ovaries (one 

 bi-lobed), vitellaria, central uterine stem, 

 cirrus and vas deferens (above), vagina 

 (below), testes (scattered), longitudinal and 

 transverse excretory vessels. 



FIG. 236. Head of Tania soliuni. 



exist; thus they may reach the abdominal cavity and the urinary 

 bladder, or they may be found in a so-called worm abscess of the 

 peritoneum ; occasionally, in vomiting, single segments or several 

 together may be brought up. Exceptionally it induces severe anaemia. 

 The larval stage (Cysticercus cellulose?) that gives rise to Tcenia 

 solium lives normally in the intramuscular connective tissue and 

 other organs of the domestic pig, but it is known to exist also in 

 a few other mammals, such as the wild boar, the sheep, 1 the stag, 

 dog, cat, brown bear and monkey, as well as in man. The cysticercus 



1 The larvae which on rare occasions are found in the muscular system of sheep are either 

 strayed specimens of Cysticerctts tcnuicollis, which normally develop in organs of the 

 abdominal cavity, and appertain to Tania marginata of the dog, or actually Cysticercus 

 (Cf. Bongert, in Zeitschr. /. Fleisch- u. Milchhyg., 1899, ix, p. 86.) 



