62 ANIMAL PARASITES. 



know nothing with certainty. Onlv this is ascertained, that 

 during the first fourteen days after the administration the yellow 

 streaks are extremely large and numerous in all those organs 

 which constitute the favorite dwelling place of one of these 

 cestoid worms in its second stage of development, but that in two 

 or three months they have generally disappeared so completely 

 (probably by absorption) that it is difficult to discover any traces 

 of them. 



In the third or fourth week, when the young brood of 

 Cysticercus pisiformis measures about 2 millim., and that of 

 Ccenurus is about the size of a large pin's head or small lentil, 

 we may see, according to Leuckart, beneath the structureless 

 epidermis a layer of annular, transverse, and another of longi- 

 tudinal, muscular fibres. The longitudinal fibres are parallel 

 and tortuous, and may subsequently be isolated in band-like 

 streaks about O0019 millim. in breadth. Then follow fatty 

 structures, and then the medullarv substance. The latter con- 

 sists of clear vesicles, combined with a tenacious albuminous 

 substance, fat and molecules, to form a layer. At the point 

 where the head is to be formed (therefore usually at the anterior 

 end) a turbidity or condensation is now produced, by the aggre- 

 gation of small nucleated cells, in great quantity, in the interstice 

 between the muscular and medullary layers. This is the first 

 foundation of the head of the tape-worm (PI. I, fig. 8, a — g). 

 Opposite to this turbidity or inflation a pit or impression (a sort 

 of perforation) is observed externally, the inner wall of which 

 is formed by the inverted epidermis, and which passes through 

 nearly the whole depth of the globular foundation of the head. 

 The latter appears like a peg firmly attached to the inner wall 

 of the worm, and hanging down into the vesicle, sometimes per- 

 pendicularly, and sometimes more obliquely {Cyst, cellulose), to 

 which a flask-shaped cavity, with a short neck, passes through the 

 perforation. Goeze compared this position of the head to the 

 light in a lantern. In the cell-mass of the tubercle of the head 

 two layers are now found : 1, a peripheric layer, which grows into 

 a fibrous, muscular pouch (receptacle of the central mass of the 

 foundation of the head, the true receptaculum capitis, under which 

 name, however, Yon Siebold understands the caudal vesicle); 

 and 2, a central layer, or the central mass of the head. 



In the latter, and especially in its upper half, calcareous 

 deposits make their appearance but sparingly at first. Two or 



