348 LUNGS AND DIAPHRAGM CHAP. 
then a larger fourth, after which comes the dilated commence- 
ment 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 lver 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 Rumuin- 
ant’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. 
The lungs are remarkable for their unlobulated character; in 
this they agree with the lungs of the Sirenia. The thoracic 
cavity in which they lie is barrel-shaped, and not, as is usual in 
terrestrial mammals, boat-shaped, 7.e. narrower sternally than 
above. The alteration of the shape of the thoracic cavity is 
associated with the aquatic life; so at any rate the fact that it is 
also marked in Seals and even in the Otter seems to show. The 
- Whales are also characterised by the great obliquity of the 
diaphragm, which is extremely muscular. In this character 
again we find an agreement with the Sirenia, and also with 
other aquatic mammals; it is not therefore a character of 
Whales so much as evidence of an adaptation to the aquatic life. 
The advantage is, it appears, in the increased capacity of the 
thoracic cavity, and the consequent greater possibilities of expan- 
sion of the lungs, which it must be remembered serve as 
hydrostatic as well as breathing organs. 
Some of the internal arteries of Whales break up into 
retia mirabiha. Their kidneys are lobulated; whether this has 
