490 HISTORY OF CYSTICEKCUS CELLULOSE. 



places and in other animals, as in man. Its occurrence, in the pig at 

 least, is usually 'very abundant. The caudal bladder is of moderate size 

 (8-10 mm.), and in the muscles has an elliptical form, the longest diameter 

 being in the direction of the course of the fibres. It contains a spirally 

 rolled and much wrinkled head-process. 



The species which we have just attempted to characterise, and 

 have designated by Linne"s name Tcenia solium, is by no means identi- 

 cal, as we have already seen, with the similarly named species of the 

 former helminthologists. " The common human tape-worm," to which 

 they gave this name, is a collective species, which includes both 

 Rudolphi's hook-bearing Tcenia solium and the hookless T. saginata. 

 Although both species are even yet frequently included in one, especi- 

 ally in foreign countries, we do not require to prove, after the fore- 

 going discussion of the history and peculiarities of T. saginata, that it 

 is justifiable and even necessary to regard them as two markedly 

 distinct species. The size, armature, uterine structure, and develop- 

 ment exhibit such characteristic features in either species that a 

 union of the two is impossible. It is especially the mode of develop- 

 ment which decides the matter, for it shows that the differences of 

 structure which were formerly supposed to be due only to some sub- 

 sequent variation, are present from the first. 



Origin and Development of the Bladder- Worm of the Pig, 

 (Cysticercus cellulosie, Auctt.). 



To Kiichenmeister is due the permanent merit of having first dis- 

 covered the relations between the hook-bearing Tcenia solium and 

 the common bladder-worm of the pig the Cysticercus cellulosce of 

 earlier helminthologists and of having thereby given a proper direc- 

 tion to our views regarding the life-history of this parasite. What 

 induced Kiichenmeister to claim the bladder- worm of the pig as the 

 larval state of the tape -worm, was principally the structure of the head 

 and hooks, which so perfectly correspond in the two forms, that the 

 most careful investigation can establish no differences between them. 1 

 The differences in pigmentation which are occasionally observed, and 

 which consist mainly in the head of the bladder -worm being of a 

 lighter shade, or indeed entirely without colour, can form no obstacle 

 to an association of the forms, especially as it is well known that the 

 adult tape-worms exhibit many variations in this respect. 



Kiichenmeister's statements had of course the effect of defining in 

 a more satisfactory manner the question regarding the origin of Tcenia 



1 " Ueber Cestoden im Allgemeinen," pp. 78, 89, 1853. 



