Atlas and text-book of dentistry including diseases of the mouth / by Gustav Preiswerk. Edited by George W. Warren.

  • Preiswerk, Gustav
Date:
1906
Catalogue details

Licence: Public Domain Mark

Credit: Atlas and text-book of dentistry including diseases of the mouth / by Gustav Preiswerk. Edited by George W. Warren. Source: Wellcome Collection.

Provider: This material has been provided by the University of Toronto, Harry A Abbott Dentistry Library, through the Medical Heritage Library. The original may be consulted at the Harry A Abbott Dentistry Library, University of Toronto.

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    Aside from the function of acquisition and mastication of food, teeth serve occasionally for other purposes. It is known for instance that the stallion has a hook tooth which is not found in the mare. A similar condition is found in musk deer. His teeth are his strongest weapon and he employs them to defend iiis mate. According to the laws of reciprocal relation, the canine teeth of the horned deer decreases in size as the horns grow larger, until finally the function of defense is transferred from the teeth to the horns. Animals must frequently remove obstructions from their paths, for this purpose they are supplied with long projecting tusks. Such animals are the mammoth, the elephant, the walrus, the hippopotamus and the male narwhal, which also uses them in defense when rutting. According to the demands made upon them the incisor teeth present many variations in form. To fulfill their function the incisors of all gnawing animals are consider- ably elongated. They are somewhat curved and in order to have sharp edges, oidy the front surface is covered with enamel. To this class belong the majority of the rodents, tillodonts, allotheriaj, and the diprotodontic ani- mals of prey. The before mentioned tusks of the elephant and narwhal are also differentiated forms of incisors. In pigs the lower incisors grow horizontally upward and forward, a formation necessary to grub nourishing roots, while the lower incisors of certain members of the lemuridous tribe of monkeys are finely niched that they may be used as combs in their daily toilette. The sirenia are characterized by large upper incisor teeth with which they pull uj) various water plants for their nourishment. When an incisor tooth develops excessively in size, the remaining incisors are usually fewer in miniber. Hence we may find that in many animals of the proboscidian type, the lower incisors hav(! com])lctely disappeared. This phenomena may occur, however, in the absence of such a condition, for examph^ we know that the ruminantia, the dinocerata and the chalicotherida), have no ui)per
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