288 



THE ANIMAL PARASITES OF MAN 



The same doubt exists here also as to the nature of the parenchyma. 

 Recent authors consider that it consists of highly branched cells, the 

 processes of which ramify in all directions. These cells lie in a non- 

 cellular matrix containing fluid vacuoles. This matrix spreads in 

 between and so breaks the continuity of the epidermal cells. 



In the parenchyma of almost all the Cestodes there are found in 

 adult specimens, as well as in larvae, light-refracting concentrically 

 striated structures, of a spherical or broad elliptical shape, which, on 

 account of their containing carbonate of lime, are termed CALCAREOUS 

 CORPUSCLES (fig. 184, C.). Their size, between 3 //, and 30 /x, varies 

 according to the species ; their frequency and distribution in the paren- 

 chyma also varies, but they are chiefly found in the cortical layer. 



Ex.v. 



L.m. 



L.m. 



Sc.c. 



Sm.f. 



FIG. 185. Half of a transverse section through a proglottis of Tania crassicollis . 

 Cu., cuticle; Ex.v., external excretory vessel, to the right of which there is the smaller 

 internal one ; T., testicular vesicles ; L.m. longitudinal muscles (outer and inner) ; M.f., lateral 

 nerve with the two accessory nerves; Sc.c., subcuticular matrix cells; Sm.f., submedian 

 nerve; Tr.m., transverse muscles; Ut. t the uterus, and the middle of the entire transverse 

 section. 44/1. 



They are the product of certain parenchymatous cells, in the interior 

 of which they lie like a fat globule in a fat cell, but according to 

 others they are intercellular in origin. 



The MUSCULAR SYSTEM of the proglottids is composed of (i) the 

 subcuticular muscles (figs. 184 and 185), as a rule consisting of a 

 single layer of annular muscles ; (2) longitudinal muscles ; (3) dorso- 

 ventral fibres extending singly from one surface to the other, and 

 at both ends expanding in a brush-like manner, and inserted into 

 the basal membrane, consisting of an outer, more numerous, and an 

 inner, less numerous but more powerful layer (the number of bundles 

 in this layer being in certain cases of specific importance) ; (4) trans- 

 verse fibres, the elements of which penetrate to the borders of the seg- 

 ments, thus passing through the longitudinal muscles and reaching 



