. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 24:2 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the lower jaw may be depressed is very much greater than in the herbivora ; in the latter, as in the horse, eight to ten centimeters being the extent of separation of the lower from the upper incisors. The digastric muscle is comparatively feeble, and would appear to pull the jaw back, but really it tends to advance it, since it is a lever of the third class. In the hare, rabbit, and ox the digastric mus
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 24:2 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the lower jaw may be depressed is very much greater than in the herbivora ; in the latter, as in the horse, eight to ten centimeters being the extent of separation of the lower from the upper incisors. The digastric muscle is comparatively feeble, and would appear to pull the jaw back, but really it tends to advance it, since it is a lever of the third class. In the hare, rabbit, and ox the digastric muscle has only one belly, and in the ox is joined to the same muscle of the opposite side by transverse muscular fibres; in the dog there is no intermediary tendon in the digastric muscle. The development of the digastric de- pends upon the character of the food of animals. In the horse, sheep, and ox, where it is small, it is a double muscle, and is inserted more anteriorly in the lower jaw than in carnivorous animals, where it is large. The conditions, therefore, are most favorable for its action in herbivora on account of its different insertion. This muscle antagonizes the temporals, masseters, and pterygoid Fig. 92.—Head of Solipede—Hokse. (Biclard.) The representative of the digastric in the lower vertebrates, as in reptilia, according to Mr. G. E. Dobson, is a bundle of muscular fibres arising from the occiput and inserted into the posterior extremity of the mandibular ramus, its functions being simply those of drawing the angle of the mandible backward and upward, and so separating the jaws in front. This is also its form and function in birds and most mammals, though in man, monkeys, and rodents the muscle is made up of two bellies with an intermediate tendon, which is often connected ty ligament with the hyoid bone. Mr. Dobson has traced an interesting connection between the mode of feeding and the type of the digastric muscle. In the group of animals in w
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