ALIMENTA11Y CANAL OF CKTACEA. 453 



beset with small rugae. A number of large irregular projections 

 surround the aperture leading to the second cavity, and are 

 calculated to prevent the passage therein of any substances save 

 such as are of very small size. Notwithstanding the nature of 

 the lining membrane the digestive processes are considerably 

 advanced in the first cavity, which does not act simply as a reser- 

 voir. It is probable that the secretion of the second stomach 

 regurgitates into the first and assists in producing the dissolution 

 of the fishes, the remains of which are usually found in it. The 

 thick epithelial lining terminates abruptly at the small orifice 

 leading into the second stomach, ib. b. The interior of this cavity 

 presents a series of close-set longitudinal wavy rugae, laterally 

 indented into one another. The internal layer is thick, and 

 mainly consists of unusually long gastric tubes perpendicular to 

 the two membranes which enclose them. The membrane next 

 the cavity of the stomach is smooth; the one external to the fibres 

 is a vascular and cellular tunic, and is invested by the layer of 

 muscular fibres, continued from the preceding cavity. The com- 

 munication with the third stomach is near the lower end of 

 cavity, b. The third compartment is a small round vascular 

 cavity, into which the second opens obliquely : it is lined by a 

 smooth and simple villous tunic : it is not visible exteriorly, and 

 does not exceed an inch in length in the Porpoise, but in the 

 Hyperoodon is about 5 inches long. The fourth cavity, ib. c, c, 

 is long and narrow, and passes in a serpentine course almost like 

 an intestine ; the internal surface is smooth and even, but villous. 

 It opens on the right side into the duodenum, ib. d, which is 

 much dilated. The pylorus is a smaller opening than that be- 

 tween the third and fourth cavities, 1 



In Balcenoptera the oesophagus enters obliquely at the back 

 part a little beyond the upper end of the first cavity : the second 

 cavity is larger and longer, in proportion to the first, than in 

 Phoccena : the rugae are longitudinal, very deep, and here and 

 there united by cross bands. The third cavity is very small, 

 and, as in the Porpoise, appears only to be a passage between the 

 second and the fourth. The latter is more definitely divided into 

 two successive cavities. 



The duodenum commences in all Cetacea, by so considerable 

 a dilatation that it has been reckoned among the divisions of the 

 complex stomach. In the Porpoise it soon contracts to the 



1 xx. vol. i. p. 175, no. 569 c. This description I appended, together with the other 

 paragraphs between brackets, to the AxtCctacea (cli"), the translation of which 

 was confided to me by the Editor. 



