An introduction to the study of mammals living and extinct / by William Henry Flower and Richard Lydekker.

Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to the study of mammals living and extinct / by William Henry Flower and Richard Lydekker. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the Ehinoceros, the inter-digital glands of the Sheep and many Euminants, and numerous others. In some of these cases the glands are peculiar to, or more largely developed in, the male; in others they are found equally developed in both sexes. II. DENTAL SYSTEM The dental system of mammals may be considered rather more in detail than space permits for some other portions of their structure, not only on account of the important part it plays in the economy of the animals of this class, but also for its interest to zoologists as an aid in the classification and identification of species. Owing to the imperishable nature of their tissues, teeth are preserved for an indefinite time, and in the case of extinct species frequently offer the only indications available from which to derive an idea of the characters, affinities, and habits of the animals to which they once belonged. Hence even their smallest modifications have received great attention from comparative anatomists, and they have formed the subject of many special monographs.-^ Teeth are present in nearly all mammals, and are applied to various purposes. They are, however, mainly subservient to the function of alimentation, being used either in procuring food, by seizing and killing living prey or gathering and biting ofi portions of vegetable material, and more indirectly in tearing or cutting through the hard protective coverings of food sub- stances, as the husks and shells of nuts, or in pounding, crushing, or otherwise mechanically dividing the solid materials before swallowing, so as to prepare them for digestion in the stomach. Certain teeth are also in many animals most efficient weapons of offence and defence, and for this purpose alone, quite irrespective of subserviency to the digestive process, are they developed in the male sex of many herbivorous animals, in the females of which they are absent or rudimentary. Teeth belong essentially to the tegumentary or dermal system of organs, and, as is well seen in the lower vertebrates, pass by almost insensible gradations into the hardened spines and scutes formed upon the integument covering the outer surface of the body; but in mammals they are more specialised in structure and limited m locality. In this class they are developed only in the ^ L. F. E. Rousseau, Anatomic comparie du Systhne dcntaire chez VHomme et ton^ZT''^''^' ^«ma««;, 2d ed., 1839 ; F. Cuvier, DesDcntsdcs Mammiflrcs 1840 « r TT- rrf7' '^^''mues, 1822-25 ; R. Owen, Odontography, iitol: III' ^^^^f' 1855 ; C. S. Tomes, Manual of dIuL anatomy, Rwnan and Comparative, 3d ed., 1889.