On account of its complication the stomach[233] has been compared to that of Ruminants--it has even been alleged that Whales "ruminate"--but the comparison will not hold good. Nor, on the other hand, is there a very close resemblance to the equally-complicated stomach of the Sirenians. The Rorqual has a stomach with as few compartments as any. The only Whale which appears to have fewer is _Balaena mysticetus_, where there are but three. In the Rorqual the oesophagus opens into a more or less globular sac; from the upper end of this, _i.e._ close to the entry of the oesophagus, arises the second chamber, long and narrowish; then follows an extremely short third sac, {348} then a larger fourth, after which comes the dilated commencement of the small intestine. The latter might be regarded as a chamber of the stomach were it not for the fact that the ducts of the liver and the pancreas open into it. This represents one type of the Cetacean stomach, which seems to be found in all Whales except the Ziphioids. In the latter, the oesophagus opens into the first compartment as usual; but the second division of the stomach arises not close to the entrance of the oesophagus, but at the opposite end. It would seem, therefore, as if the first division of the stomach, found in most Whales, were missing in Ziphioids. This way of looking at the matter is confirmed by the fact that in _Hyperoodon_ a remnant of the missing first stomach is found in the shape of a small diverticulum of the oesophagus just before it enters the stomach. The essential difference between the Whale's and the Ruminant's stomach is this: in the latter the stomach is primarily divided into two portions, of which the first is non-digestive and is clothed with oesophageal epithelium. The second, the abomasum, is the digestive region. The first part is again divided into three compartments. In the Whales, on the other hand, it is the digestive part which is again subdivided, while if the first part is divided it is not markedly so as in the Ruminants.