442 CETACEA. 



opening being more dorsal than the left. The opening has acrescentic lower border, 

 the concavity of which looks np the oesophagus, and at the opening a portion of 

 the mucous membrane of each cavity is opposed to that of its fellow. The 

 common orifice has a capacity, in an individual about 6 feet long, of about 2 inches 

 in breadth, when moderately distended. The two cavities are united to each other 

 only immediately below the common opening, and in the individual already men- 

 tioned the attachment is 1'60 inch in one direction and 1-50 in another. 



Microscopic characters of the membrane of the first cavity. — A portion of the 

 adult stomach, in which a layer of the mucous membrane was peeling off, showed 

 this, under a low power of the microscope, as divided into two parts by a dark hne 

 corresponding to the line of desquamation, although the two were still connected 

 together. The external there appears much more dense than the internal layer, and 

 the former is of a uniform consistence, giving no indications of separation into 

 thinner layers. It must be borne in mind that this desquamation of a surface layer 

 of this cavity cannot be regarded as a post mortem phenomenon, for in the specimen 

 in question the stomach was removed as soon as the animal died ; even by that time 

 the limit of effete mucosa had been already indicated at those points where the 

 tissue had not become separated. The same condition I have observed in more 

 stomachs than one. 



This natural shedding of a superficial layer of the membrane of this first gastric 

 cavity receives elucidation on a further study of the constituents of the entire wall 

 of the organ being made. Consult PL XXXVI, figs. 12 and 13, and compare fig. 14 

 of a corresponding piece of the same gastric cavity of Orcella, already described. In 

 that of Flatanista under a low magnifying power (Pig. 12), the epithehal layers^ 

 desquamative and subjacent, are but of moderate thickness, relative to that of the 

 entire wall of the stomach. The body of the connective and vascular tissue beneath 

 these is on the contrary very thick, while the muscular and serous coats are of 

 medium thickness. Under a much higher power, and thus greatly enlarged (Eig. 13) 

 the characteristic features are easily resolved. The free internal surface is composed 

 of a stratified mass of horny epithelial scales {ep) in different stages of- development. 

 Layer after layer of these then must be given off as digestion proceeds, and the 

 phenomenon of desquamation above mentioned must be, as inferred, a natural 

 process of constant occurrence. 



The second layer in close continuity with the first is analogous to the columnar 

 cell-layer already described as existing in the first gastric cavity of Orcella (Eig. 

 14, eg). It is, indeed, only a continuation downwards of the epithelium, the cells 

 assuming less of a horizontal, and more of a vertical, position. In Tlatanista, moreover, 

 as contradistinguished to Orcella, the descending columns are far shorter, broader, 

 •and club-shaped. In fact, the columno-epithehal double layers of the former genus 

 altogether are little more than half the depth of the latter. This coat of the first 

 stomach in both animals may aptly be compared to the cuticular layer of the skin, 

 the deeply placed prolongations being nothing more or less than a mucous or Mal- 

 pighian layer. They are not, in any sense, true gastric secreting follicles, as in the 



