LESSON 48.] NUTRITION IN FISHES AND EEPTTLES. 1*71 



The same short, broad, square-shaped organ that belongs per- 

 sistently to this portion of the intestinal canal in all the warm- 

 blooded animals, is equally characteristic of the duodenum of a lowly 

 Batrachian ! 



The folds that were transverse in the duodenum, become lon- 

 gitudinal in the ileum, and display a beautiful arrangement of capil- 

 lary blood-vessels (Fig. 273), as shown in the figure, copied from an 

 injected preparation of the tissue. The large intestine (colon), al- 



FIG. 272. Fio. 278. 



Ileum of Frog. Duodenum of Toad. 



though destitute of folds, presents a fine example of capillary dis- 

 tribution, and is shown in Fig. 274. 



The mucous membrane of the large intestine presents great uni- 

 formity in both frogs and toads, and consists of a plexus of capillary 

 blood-vessels, which appear to cross the larger vessels of supply and 

 return (arteries and veins) which are situated in the sub-mucous tissue. 



The mucous membrane is so thin and transparent in these ani- 

 mals, that the larger vessels can be distinctly seen in a well-injected 

 preparation, through its parietes; this is shown in the large intes- 

 tine of the Frog, Fig. 274. 



750. The Batrachian reptiles (batrachos, a frog), which include 

 the frogs and toads, are not amphibious they are air-breathing an- 

 imals, and cannot respire at all under water. If a frog be kept be- 

 neath the surface of the water he dies, in 



,. f . FIG. 274. 



not exceeding four hours. 



751. There are reptiles, however, 

 supplied with permanent gills, for aquat- 

 ic respiration, and lungs, for breathing 

 air, and these constitute truly amphibi- 

 ous animals. The ponds of this country 

 teem with a very interesting amphibious 

 reptile the Menobranchus (permanent 

 gills), usually called " the mud sucker." 



752. In form it is somewhat Lizard-like, having a long body, four 



