102 



ANIMAL PHYSIOLOGY. 



[LESSON 29. 



FIG. 175. 



FIG. 176. 



the Cysticercus is the young. The head of the latter animal is, in 

 every respect, so identical with the former, that a figure 

 of it is unnecessary. 



508. Two species of Distoma (dis, two ; stoma, 

 mouth) infest the human subject D. hepaticum, found, 

 as the specific name indicates, in the liver, and D. lan- 

 ceolatum ; of these animals, the former is also very abun- 

 dantly found in the Pig. It is also sometimes found in 

 large quantities infesting the liver of the Sheep, and 

 in them it causes the rot. They are supposed to take 

 up Planariae with the water they drink, which, under 

 D.tepaticum. a i tere( j circumstances of position, becomes a Distoma. 

 509. The nutrimental canal is very simple in both these animals. 

 In D. hepaticum (Fig. 175), a represents the suctorial mouth, b the 

 anterior sucker ; the second is imperforate, and is simply an organ 

 of adhesion. The alimentary canal is continued from the mouth for 

 a short distance as a single tube, and then divides ; the 

 divisions run parallel with each other, and surround the 

 ventral sucker, which-is placed between c, c, and is also 

 for the sole purpose of adhesion ; the parallelism of the 

 tubes is then continued to the caudal extremity. Each 

 tube gives off several branches from the outer, and but 

 few from the inner side ; many of these branches are 

 ramified, and all of them terminate in blind extremities 

 near the margin of the body. 



510. In Distama lanceolatum, the suctorial pores 

 are larger than in D. hepaticum ; the anterior sucker is 

 perforated by the mouth (Fig. 176, a), and the alimen- 

 tary canal, commencing by a kind of pharynx, is con- 

 tinued as a very slender tube (c) for a short space, and 

 bifurcates, each division being continued without rami- 

 fication, on each side of the body to the tail, where it 

 ends in a blind extremity (d). The ovaria are seen at 



y, and the oviducts at g. The second sucker is at b. 



511. It is a very remarkable fact that nearly all 

 the animals parasitic in man, are found in only one 

 other animal the Pig ; and whether we obtain them 

 directly from itj or whether it be another point of close 

 affinity between the animal in question and humanity, 



has yet to be determined. 



Dist ia 1 tum nceo " 



