MAMMALIA, 547 
The molar teeth of elephants consist of many (up to twenty- 
four) successive ridges, each with its roots. Hence it is 
possible, by an appeal to the principle of cusp-multiplica- 
tion followed by separation, to suggest an origin for the 
great number, as well as the simple structure of the ceta- 
ceous teeth. 
Behind the mouth the larynx and glottis are produced 
from the ventral wall of the cesophagus upwards as a long 
cylinder into the base of the internal nostrils, a striking 
adaptation which enables the porpoise to open its mouth 
under water and even to swallow whilst breathing. A 
similar modification is found in young Me/atheria, in this 
case enabling them to breathe and swallow milk at the same 
time. 
Returning to the porpoise we find that it possesses a 
complex stomach, a rare possession for a flesh-eater. The 
first and largest chamber is a storage sac with no glands, 
probably a mere dilatation of the cesophagus: this is 
followed by a smaller receptacle with fundus (tubular) 
glands and folded walls: a very small globular third 
compartment passes into a long vermiform fourth part 
which has pyloric glands and leads into the duodenum. 
Reverting to the skeleton, we find the cervical vertebree, 
seven in number, are short and fused together. A flexible 
neck, far from being a necessity, is rather a drawback to an 
aquatic animal, rigidity of the anterior end being imperative 
for rapid locomotion. The dorso-lumbar vertebre are hard 
to define for there is no sacrum, but between the first 
caudal and the last cervical there are about twenty-seven in 
number, the first thirteen, as in most mammals, bearing 
ribs. The transverse processes are prominent, as also are’ 
the neural spines. The former arise from the side of the 
centrum in the last lumbar, but higher and higher up on the 
neural arch as one proceeds forwards. The round disc- 
shaped epiphyses are very conspicuous. The hindermost 
of these dorso-lumbar are probably the former sacral verte- 
bree, but as the ilia have atrophied there is no certainty. 
The caudal vertebre are numerous (30-31) and, as in 
the kangaroo, bear paired chevron bones on their under 
surface. It is usually assumed that the caudals commence 
with the chevron bones, The fore-limb and girdle are 
