742 



DESCRIPTION OF BOTHRIOCEPHALUS CORDATU8. 



exhibited by the head (Fig. 394). The shape of the head of course 

 varies, but may be generally compared to the heart in a pack of 

 cards, or to an arrow-head. The flattening increases gradually 

 towards the point, but is, on the whole, not conspicuous, and least so 

 in the posterior half, where the rudiment of the subsequent lateral 

 margins of the body is recognisable. 



The anterior half is distinguished, not only by its flattening, but 

 also by the depth of its marginal grooves, which is so considerable, 



that they are separated from one 

 another only by a thin partition. On 

 the other side of the middle of the 

 head, the depth and width of the 

 grooves gradually decreases, until a 

 shallow furrow alone remains. With 

 the depth of the grooves the more or 

 less free development of the limiting 

 lips is associated. That the latter, 

 even where most independent, are 

 without any proper musculature, has 

 been already mentioned as character- 

 istic of the genus Bothriocephalus. 

 The fact is readily demonstrated in 

 transverse sections, in which one can 

 also convince one's self of the general structural and histological 

 resemblance between the head and the rest of the body. In the 

 head, as elsewhere, a median layer and a peripheral muscular sheath 

 are distinguishable, both but slightly diverging from the ordinary 

 type. The internal wall of the marginal grooves is, of course, formed 

 from the cortical layer, which is here so thick that the middle layer 

 in the anterior half of the head is entirely displaced by the layer 

 connecting the two lateral surfaces. In the middle layer, besides 

 numerous calcareous corpuscles, the two nerve strands can be 

 recognised, disposed opposite to one another in the direction of the 

 smaller diameter. 



The structure of the generative organs does not differ typically 

 from that of B. latus ; and I have not been able to elucidate their 

 development. The ova closely resemble those of the Swiss tape-worm, 

 but are on an average somewhat larger (O075 to 0*08 mm. long, by 

 0'05 mm. broad). 



It was to be expected from the analogy with B. latm, that B. 

 cordatus would liberate its joints in groups, and not singly. The 

 specimen (Fig. 397) obtained from the patient, as above described, 

 most clearly suggested the occurrence of this process. At a distance 



FIG. 400. Transverse sections of 

 the head of Bothriocephalus cordatus ; 

 A, before, B, behind the middle. ( x 

 about 20.) 



