FASCIOLA HEPATIOA. 151 



Beneatli the skin are found numerous bands of muscular fibres, 

 in wbich four separate groups may be recognized more or less dis- 

 tinctly. They have been described as so many layers, but they are 

 not readily separable from one another. Well-marked longitudinal 

 and transverse fibres may be seen at all parts of the body, and two 

 series of diagonally directed fibres, some passing downwards from 

 right to left, and others from left to right. The fibres themselves 

 belong, of course, to the non- striated kind of muscle, and consist of 

 narrow, fusiform cells, measuring from ^7 to ^^ of an inch in length, 

 and having a breadth of about the ^ of an inch. They are flattened 

 throughout, and display a single oval nucleus, which refracts light 

 rather strongly. Towards the anterior end of the body all the 

 groups of muscular fibres are more strongly developed. 



The general parenchyma of the fluke consists of rather loosely- 

 connected and irregular polygonal cells of unusually large size, 

 measuring from sh to afr of an inch in their greatest diameter 

 (Leuckart). The margins are well defined, and there is a distinct 

 nucleus (g^o " to 2^0 ') presenting a finely granular appearance. A clear, 

 transparent, homogeneous fluid occupies the interior of the cells. 



AU the tissues of the body possess highly contractile properties, 

 but the fluke is undoubtedly aided in locomotion both by the oral 

 and ventral sucker. These organs may be regarded as specialized 

 developments of the transverse and longitudinal system of fibres, 

 which have become exaggerated to serve a distinct purpose. The 

 oral sucker is perforated in the centre, and communicates with the 

 oesophagus, but the ventral is imperforate, consisting simply of a 

 cup-shaped disk, forming a sort of alveolus with a thick, circular, 

 prominent margin. In both, two distinct sets of fibres are distin- 

 guishable, that is, a circular series and a radial group. These 

 bundles interlace one another, forming powerful sphincters, which, 

 when applied to any soft surface, must, during full action, produce 

 a very considerable vacuum in the centre of the disk. The oral 

 sucker difiers only from the ventral in respect of size and incom- 

 pleteness at the lower part, in which latter situation it is either 



