ITS SPECIFIC DISTINCTNESS. 741 



Grassi thought, indeed, that Linne's Tcenia lata might be referred 1 

 to our Bothriocephalus cordatus, but from the description and figures 3 

 it seems to me as though it differed only in its greater contraction 

 from the more elongated T. vulgar is, and thus simply represented a 

 much contracted specimen of T. lata. Of T. lata it is indeed said 

 " rarissime in hominibus vermis observatur, vulgatissimus auteni in 

 canibus ; " while in regard to T. vulgaris nothing is said of its occur- 

 rence in the dog, but merely, " vulgatissimus (vermis) inter Tsenias 

 homines infestantes ; " but this alone is not enough, and the differ- 

 ences between the species as noted by Linne may perhaps be due 

 to the worms from the dog having been examined in a lively and 

 contractile state, while those from man were observed only when 

 exhausted or even dead. The descriptions indeed suggest this 

 supposition. 3 This much, at any rate, is certain, that the description 

 of T. lata affords no decisive proof of its identity with our B. cordatus. 

 The head, which ought to form the primary object of investigation, 

 is not described either in T. lata or T. vulgaris, and was perhaps not 

 even seen. 



Be that as it may, a denial of the specific distinctiveness of B. 

 cordatus seems to me henceforth impossible. Even the separated 

 joints can be readily distinguished from those of B. latus, less perhaps 

 on account of their form, though that, too, is diagnostic, than on account 

 of the calcareous corpuscles, which are as abundant in the Greenland 

 species as they are rare in the Swiss or Eussian tape- worm. They 

 are thickly distributed through all the layers of the body, and some- 

 times attain a size of 0*028 to 0*03 mm. The peculiarity in the 

 structure of the uterus has been already noted. Similarly the 

 stronger development of the muscles, especially of the longitudinal 

 muscles in the cortical layer, must be noted as characteristic of B. 

 cordatus, and this explains the striking contractility of the worm, as 

 also the large size of the cirrhus-pouch (0'6 mm. long by 0'43 mm. 

 broad), as compared with that of B. latus. These are, however, points 

 of detail, and, for diagnostic purposes, unimportant in comparison 

 with the structure of the head and anterior portion of the body. 



In the larger worms the head has a length of 2 mm., and a pro- 

 portionately large breadth. Viewed from the flat side, the anterior 

 half appears pointed, while the lateral portions project posteriorly, 

 more or less like wings, according to the degree of contraction 



1 Ann. univ. di Med., vol. ccli., 1880. 



2 " Amoenit. Acad.," vol. ii., p. 71, Fig. 3. 



3 Thus it is said of T. lata, " Dum adhuc vivus est et se extendit, uno alterove loco 

 filifonnis evadit, et articuli iis in locis graciles fiunt, atque post ejus mortem lati sunt," 

 while no mention at all is made of the living state of T. vulgaris. 



