WHALES AND DOLPHINS. 



so accurately as to close it completely. The 

 animal can thus breathe merely by raising 

 the top of its head to the surface of the water, 

 and can swallow its food in the water without 

 a drop of liquid penetrating into the wind- 

 pipe and lungs, since the fragments in their 

 way down the gullet pass round the larynx 

 where it is inserted into the posterior part of 

 the nasal passage. The external passage of 

 the ear (external auditory meatus) opens on 

 the surface of the skin by a very narrow, 

 aperture; even in a large whale it is scarcely 

 possible to introduce a goose-quill into the 

 opening. The eyes are often placed so far 

 behind and at the side that they lie im- 

 mediately behind the corners of the mouth. 

 They are not inclosed in a bony orbit, but 

 only by a very thick white skin. The pupil 

 itself is not larger than in an ox. 



The lower jaw forms a more or less ex- 

 panded pointed arch, or even a longish beak. 

 There is scarcely any joint behind, and the 

 coronoid process, or ascending part of the 

 lower jaw to which the muscles of mastication 

 are attached in other mammals, is almost 

 entirely wanting. We will afterwards return 

 to the dentition. 



All these modifications lead to very peculiar 

 arrangements in the structure of the skull, 

 but these we will not enter upon in detail at 

 present. Let it suffice to say that the petrous 

 bone, or bone containing the inner ear, is 

 separate from the other bones of the skull, 

 and the skull itself is not symmetrical, one of 

 the halves, usually the right, being always 

 larger. This want of symmetry is often 

 more marked in one individual than in another 

 of the same species, but always exists. 



The neck is indistinguishable in the living 

 animal, the head, which is very broad behind, 

 being attached to the trunk without the 

 slightest appearance of constriction. In the 

 skeleton the usual number of neck-vertebrse, 

 seven, are indeed present, but they soon be- 

 come fused with one another, wholly or par- 

 tially. The vertebrae of the trunk have the 



processes but slightly developed, and very 

 liable to become detached; those of the tail 

 have no processes. There is never any 

 sacrum, since the pelvis is wanting. 



The fore-limb forms a fin, connected with 

 the trunk by a triangular shoulder-blade. 

 The short and usually flattened upper-arm or 

 humerus is entirely buried in the flesh of the 

 body. The bones of the fore-arm, wrist, and 

 hand are firmly connected together by strong 

 sinewy tissues or ligaments without any joints, 

 and are enveloped by a tough firm skin. 

 The whole limb accordingly is movable only 

 at the shoulder- and elbow-joints. The digits 

 are indicated by rows of small rounded bones, 

 often very numerous, and the terminal bones 

 or phalanges are without nails. The hind- 

 limbs are altogether wanting. But in some 

 whales there are found some bones buried in 

 the flesh which are rudiments of a pelvis repre- 

 senting the thigh- and shin-bones, but which 

 never become developed, being found only 

 in the embryo. In most whales there are 

 also to be seen vertical dorsal fins, formed, 

 like the tail-fin, of a skin supported by a fibrous 

 and horny tissue. 



The brain is relatively small, but covered 

 with numerous convolutions. In a whale 20 

 feet in length and weighing 12,000 lbs. the 

 brain did not weigh as much as 4^ lbs. In 

 the small species, like the dolphins, however, 

 it is relatively much larger and in particular 

 much broader. 



Salivary glands are absent. Numerous 

 enlargements of the arteries and veins allow 

 of the animal remaining a considerable time 

 under water without the necessity for purify- 

 ing the blood by breathing. The teats lie in 

 deep folds of the skin on both sides of the 

 anus. The placenta is diffuse, composed, 

 as in the pachyderms, of lobes or cotyledons 

 distributed over the whole surface of the 

 ovum. 



The dentition presents very remarkable 

 differences. The teeth are never specialized, 

 always simple, and have only a single root. 



