PASOIOLA HEPATICA. 163 



believes, serve to prevent the regurgitation of the food after it has 

 distended the stomachal passages. All who have had much to do 

 with fresh living flukes must have observed a tendency to eject the 

 stomachal contents, immediately on their removal from the liver of 

 their host. The cold air — ^like the more cruel stimulus of salt 

 applied to the skin of a recently gorged leech — causes the body of 

 the fluke to contract and curl upon itself, and the animal pro- 

 bably derives some relief by allowing the food to escape by the 

 oral outlet. 



Mention of these phenomena naturally lead to the consideration 

 of the digestive system. The mouth, as we have seen, is placed 

 at the apical or lower part of the cup-shaped cavity of the anterior 

 sucker. In this situation it leads into a comparatively short 

 oesophagus (about i|g" in diameter) which subdivides into two 

 primary intestinal divisions, the point of bifurcation being situated 

 immediately above the location of the external reproductive 

 orifices. The two primary digestive tubes run downwards in a 

 parallel manner on either side of the central line, until they reach 

 the caudal extremity. During their passage downwards they give 

 ofi" a variable number of secondary tubes, which likewise in their 

 turn give ofi" others, which subdivide, more or less frequently, when 

 at length all of the branches ultimately terminate in blind coecal 

 extremities (Plate XI., Fig. 2). A few short twigs are also given off" 

 from the primary straight tubes, being directed towards the middle 

 line, where they terminate very abruptly, but frequently giving 

 evidences of an effort, as it were, on their part to develop tertiary 

 tubes. In the region of the head and neck, the secondary branches 

 are directed upwards and outwards ; lower down they diverge more 

 directly outwards, whilst at the middle and lower part of the body 

 they slant obhquely downwards toward the lateral borders. Alto- 

 gether they form a beautiful series of dendritically ramifying 

 canals, preserving on either side a tolerable, but not entirely 

 uniform, degree of regularity ; moreover, the two halves of the 

 system do not completely correspond, or, in other words, the 



