United States or Jersey ? Vote for the TOP Country of the Week !
The suspension of the lower jaw, so as to bring the teeth nearer the power, the masseter and related muscles, was a slow evolution and a great advance. The fin is more primitive than the limb; the limbs themselves display a constantly increasing differentiation of parts from the batrachian to the mammalian. There was no good ankle joint in early Eocene times.
Short hair, slightly woolly, with metallic reflections; large chest rising and falling like a smith's bellows; arms, hands, legs, feet, all worthy of the trunk. No mustaches, no whiskers, but a large American goatee, revealing the attachments of the jaw whose masseter muscles were evidently of formidable strength.
Spencer maintains that the dwindling of the parts concerned in clenching the jaw is certainly not due to artificial selection because the modifications offer no appreciable external signs. Surely hard biting is sufficiently appreciable by the person bitten without any visual admeasurement of the masseter muscles or the zygomatic arches.
The relative breadth between the outer surfaces of the zygomatic arches is conspicuously small; the narrowness of the temporal fossæ is also striking; the zygomata are very slender; the temporal muscles have left no marks whatever, either by limiting lines or by the character of the surfaces covered; and the places of attachment for the masseter muscles are very feebly developed.
The masseter muscles, which are the heavy muscles in the cheeks, and the temporal muscles, located in the region of the temples, raise the lower jaw and supply the force for grinding the food. Small muscles situated below the chin depress the jaw and open the mouth. They secrete the saliva. The salivary glands are six in number and are arranged in three pairs.
Two important muscles, the temporal, near the temples, and the masseter, or chewing muscle, are the chief agents in moving the lower jaw. They are very large in the lion, tiger, and other flesh-eating animals. On the inner side of each cheek is the buccinator, or trumpeter's muscle, which is largely developed in those who play on wind instruments.
The nucleated cells found connected with the cancellated structure of the bones, which I first pointed out and had figured in 1847, and have shown yearly from that time to the present, and the fossa masseterica, a shallow concavity on the ramus of the lower jaw, for the lodgment of the masseter muscle, which acquires significance when examined by the side of the deep cavity on the corresponding part in some carnivora to which it answers, may perhaps be claimed as deserving attention.
The nucleated cells found connected with the cancellated structure of the bones, which I first pointed out and had figured in 1847, and have shown yearly from that time to the present, and the fossa masseterica, a shallow concavity on the ramus of the lower jaw, for the lodgment of the masseter muscle, which acquires significance when examined by the side of the deep cavity on the corresponding part in some carnivora to which it answers, may perhaps be claimed as deserving attention.
If careful observations be made, it may be found that the muscles in the immediate neighbourhood of the wound are the first to become contracted; but in the majority of instances the patient's first complaint is of pain and stiffness in the muscles of mastication, notably the masseter, so that he has difficulty in opening the mouth hence the popular name "lock-jaw."
The only pug-dog's skull is that of an individual not perfectly adult; and though its traits are quite to the point they cannot with safety be taken as evidence. The skull of a toy-terrier has much restricted areas of insertion for the temporal muscles; has weak zygomatic arches; and has extremely small attachments for the masseter muscles.
Word Of The Day