SOME INTERNAL STRUCTURES 67 



it is a large storehouse ; in whales this would seem to 

 be needless. It is thought that the first stomach of 

 the whale is a chamber in which the food is to some 

 extent broken up and softened by mechanical means ; 

 it is analogous, in fact, on this view, to the bird's 

 gizzard. The muscular layers of its walls are thicker 

 than in the thin-walled rumen of the ruminant. Often, 

 too, this compartment has been found to contain sand 

 and stones, just as does the bird's gizzard, and for the 

 matter of that, the stomach of the Sea-lion. This 

 introduction of sand and stones may be accidental ; 

 but, on the other hand, its presence may be explained 

 as an accessory to the trituration of the food. It is 

 obvious that a trituration of this kind and rumination 

 are mutually exclusive. The balance of probability is 

 in favour of the former action of the first stomach. 

 But even now we have not accounted for the com- 

 plication of the true digestive stomach. It is to be 

 noticed, however, that here, as already stated, we are 

 free from any analogy with the herbivorous stomach ; 

 in the Sirenia and Ruminants this part of the stomach 

 is not complicated. It is only the first part associated 

 with the non-digestive functions of the stomach. This 



o 



problem, it is to be feared, we must leave unsolved. 

 Finally, there is the fact of the absence of the first 

 stomach in the Ziphioids to explain physiologically. 

 Dr. Jungklaus thinks that this is associated with 

 their exclusive diet of cuttlefishes, which require no 

 stomachal "mastication." Their tissues are soft, and 

 are easily digested by the digestive part of the stomach 

 without any previous maceration and pressing. 



