PLATANISTA. 443 



ordinary mammaKan digestive stomach, for they are solid compact masses of cells 

 without exterior orifice, apparently do not secrete gastric juice, and only develope 

 cylindrical epithelial cells, which latter are modified in figure, &c., as they rise to the 

 surface. In some respects they may be regarded in the light of mucous glands, the 

 stratum homologically being equivalent to the gastric or peptic glands of the mam- 

 malian stomach generally. It would thus appear the latter sort are absent in this 

 first gastric cavity, and instead, mucous glands, such as are found in quantity in the 

 cardiac area of the stomach of the horse, alone are present. This condition of things 

 recalls the coats of the gizzard of birds, where in some forms not only is there a 

 thin partial desquamation of the superficial cells, but the entire horny layer is 

 periodically shed and renewed.^ 



The submucous or alveolar layer (Fig. 13, c) of this first cavity in Tlatcmista is, 

 as usual, composed throughout of connective tissue, scattered through which are 

 spindle-shaped cells, and blood vessels and capillaries in quantity. 



The muscular layer (Tig. 13, m), in vertical section, presents fibres cut crosswise 

 and lengthwise, corresponding therefore to the different direction of the fleshy 

 bundles, and the fibro-serous layer {fs ) is unusually thick. 



Second or right cavity. — (PI. XXYI, fig. 1, 11.) — This is irregularly pyriform, 

 the stalk of the pear-like figure being the oesophagus, the body being bent to the left 

 side so that the right is much rounded and more extensive than the left, deeply 

 concave margin. It does not reach to so low a level as the first cavity, than which 

 it is less capacious. Its walls are not so firm as those of the left cavity, nor so thick, 

 neither have I ever observed it to become similar to that of the oesophagus, however 

 great may be the changes which the mucous membrane may undergo, for it is always 

 more or less rugose. It is found generally thrown into very deep folds and is densely 

 covered with fine rugse, but nearly all the former are permanent, whilst the latter are 

 transitory. Corresponding to the most concave portion of the left wall of the second 

 cavity, a permanent fold is found encircling the inside of the sac obliquely from left 

 to right, and below it there is a short strong crescentic fold stretching from the an- 

 terior on to and along the posterior wall, till on a level with the lower border of the 

 cavity. The free margin of this almost valvular fold is directed ventrally and to 

 the right side. A short way behind it, another and shorter fold stretches in the 

 opposite direction from the posterior on to the anterior wall, and has its free margin 

 directed dorsally and to the left side. These two folds are occasionally so strongly 

 marked that they almost divide the apex or fundus of the second cavity into two dis- 

 tinct chambers, but, as they are not continuous around its walls, the division is very 

 imperfect. In other states, although the folds are present, there is no appearance of 

 division of this cavity into separate chambers. 



In an active stomach the whole of the inner surface of the second cavity presents 

 a uniform structure and character throughout its whole extent. A spirit specimen 

 has a greyish-brownish tint, and the mucous membrane is thrown into an immense 

 number of well-defined, finely convoluted rugge. In this cavity, in an old female, the 



- Murie : Proc. Zool. Soc, 1874. p. 423- 



