132 



THE ANIMAL PARASITES OF MAN 



it is attached. The loosening of the fixed sucker is effected by 

 relaxation chiefly of the radial fibres, by the contraction of the 

 meridional fibres and certain bundles of muscles situated at the 

 base and in the periphery of the suckers. The connective and 

 elastic tissues between the muscles of the suckers probably also 

 take part in this process. 



Of the muscles of the organs which have developed from the 

 parenchyma muscles we may briefly mention those bundles that are 

 attached to certain parts of the genital apparatus, to the suckers, 

 to the hooks and claws, and also, at all events in Distomum 

 hepaticum, to the spines. The sheaths used for the projection of 

 the rostrum of the Rhopaliadea are also muscular. 



T. 



F.-v.s 



Md. 



Ex.v. 



FIG. 67. Half of a transverse section through Fasciola hepatica, L. 25/1. Cu., 

 Cuticle with scales; under the cuticle are circular muscles which adjoin the longitu- 

 dinal and diagonal muscles ; within the latter are the matrix cells of the cuticle ; 

 /., intestinal tube ; .the remaining similarly contoured space cavities are intestinal 

 culs-de-sac that have been transversely or obliquely sectioned ; F.v.s., follicles of 

 the vitelline sac ; Ex.v., excretory vessels ; T., testicular tubules ; Md., median 

 plane ; the fibres passing from the ventral to the dorsal surface are the muscles of 

 the parenchyma. The parenchyma itself is omitted. 



The contractile elements consist of fibres of various lengths 

 that are mostly parallel to one another, and frequently anasto- 

 mose ; a cortical substance of delicate fibres can usually be dis- 

 tinguished from an internal homogenous mass ; large nucleated 

 cells of equal size are always connected therewith, these have 

 been variously named, but have finally proved to be myoblasts ; 

 one or more of their processes are the muscular fibres. 



The MOVEMENTS of the Trematodes consist in alterations of 

 form and position of the body, as well as in creeping movements. 



