imperfectly figured in one of the Plates;[1] when inflated, it is pyriform; in the empty condition, it assumes the outline of the liver (see Plate II, Fig. 3). The biliary ducts open into the intestine, just where it is connected with the liver, by a common duct.
The small intestines make two principal convolutions, and are kept in their place by a well-developed mesentery. I could detect no trace of a pancreas. As the intestine approaches the rectum, it becomes excessively narrow, and at last ends almost by intussusception (Fig. 5); the wide and capacious rectum ends in the cloaca. Before examining the internal structure of these parts, it may be well to compare them with similar organs occurring in the salamanders. For this purpose I have selected Triton cristatus and Salamander maculosa. So far as the œsophagus and stomach are concerned, the relative size and proportions are nearly similar. The stomach is more pear-shaped in S. maculosa. In Triton, the spleen is a small, flat, oval gland, attached to the right side of the stomach by a loose fold of mesentery, but by no means closely so; in Salamander,[2] it is a long, narrow, ribbon-like body, closely attached to the right side of the stomach. In Triton, the liver is small, but divided into lobes; the gall-bladder is well developed. In Salamander, the liver is rather small in proportion, not much divided, and the gallbladder is also small. In both Triton and Salamander, the small intestine is very well developed, and in both does it contract as it approaches the rectum, which here, as in Siredon, is much wider than the rest of the intestinal canal.
In the axolotl the œsophagus is short, the mucous surface is longitudinally and finely striated, the external muscular fibres are circular, and act as a sphincter; in the stomach, the mucous membrane is continuous with that of the œsophagus, but here it is thrown into deep folds. The fine striæ of the œsophageal portion are continued; and at what may be considered as the cardiac orifice, these folds of the mucous surface are brought into such close apposition, their dimensions at this spot, too, are so greatly increased, forming four or five little protuberances; as to take the place of a valve and effectually prevent any regurgitation into the mouth. Though there are a few file-like teeth in the upper jaw, yet they serve more for organs of prehension, and cannot be of much use in mastication; and, undoutedly, the process of comminuting the food is mostly accomplished in the stomach.
In this organ, as I have said, the mucous membrane which lines the
- ↑ Loc. cit., Plate 12, Fig. 4.
- ↑ Here I would observe, that I cannot agree with Schneider, who, in his Natural History of Amphibia, has united the aquatic (Triton) with the land (Salamander) Salamanders; although in both genera the ovæ are impregnated before being laid, yet in the one (Triton), we have the eggs deposited on aquatic plants; the young Tritons, when hatched, retaining their branchiæ for a longer or shorter length of time; in the other (Salamander) we have the oviducts large and capacious, the ovæ are hatched in them, making their exit into the world almost miniatures of their parent. Surely such embryological distinctions point to at least a difference in the general—in the ordinary acceptation of this word—of these creatures.
