Another interesting feeding adaptation is present in the throat of the whale. The nostrils, instead of opening into the back of the mouth, as in land mammals, are directly connected with the lungs by a prolongation of the “windpipe” called the epiglottis, which entirely shuts off the whale’s breathing passage from the mouth. Thus the animal can swallow its food beneath the surface without danger of strangulation through getting water into its lungs.

When whales lived upon the land external ears were necessary, but as they became completely aquatic such “sound collectors” were not only of no more use but highly undesirable, because, like the useless hind-limbs, they offered additional resistance to the water; therefore the external ears were lost, but their muscles still remain about the minute ear-orifices of the present-day Cetacea.

The internal modifications which the whales underwent as they assumed an aquatic existence are fully as remarkable as the external changes. In the section on osteology it has been explained how, in living cetaceans, the entire skeleton is loosely articulated so that great flexibility and freedom of movement is given to the body, how the neck is shortened and the vertebræ have become thin and closely packed together to support the large head, and how the breast bone is reduced and the ribs so loosely articulated to the vertebral column that the huge lungs have full power of expansion. All these are necessary modifications of the mammalian skeleton which have been caused by the change from a terrestrial to an aquatic existence.

The lungs of the Cetacea are unlobulated and of extraordinary size; the diaphragm, the muscular partition which separates the thoracic from the abdominal cavity, is oblique, and the brain greatly convoluted and of a high type; the brain is especially notable for the loss of the olfactory, or smelling portions, which are of no use to an aquatic mammal.

Thus it is apparent in a review of only the most obvious changes what a wonderful example of adaptation to environment is furnished by the Cetacea.

INDEX


TRANSCRIBER’S NOTES

  1. Silently corrected obvious typographical errors and variations in spelling.
  2. Retained archaic, non-standard, and uncertain spellings as printed.
  3. Re-indexed footnotes using numbers.