DIGESTION. -r, 



It is like true bone, and contains lacunae and canaliculi. Externally 

 it is covered by dental periosteum. In old age the cement grows 

 thicker and may close up the entrance to the pulp-cavity. 



THE SALIVARY GLANDS. 



The parotid gland is named from its position near the ear. It 

 is the largest of the salivary glands. 'It extends upward as far as the 

 zygoma, downward as far as the angle of the lower jaw, and inward 

 between the ramus of the jaw and the mastoid process. The duct of 

 the parotid, called Stenos, has the diameter of a crow-quill, is two 

 inches in length, and runs across the masseter to open into the mouth 

 opposite the second molar tooth 



Fig. 10. Histology of the Salivary Glands. (LANDOIS.) 



B, Alveoii of the rested submaxillary of the dog. c, The distended, glistening 

 mucous cells, d, Gianuzzi's crescents. C, The alveoli after active secretion, 

 showing the connective tissue of the alveoli isolated at D. 



The parotid has a full supply of blood-vessels, which run through 

 it. The nerves of the parotid are the auriculo-temporal and the 

 cervical sympathetic. In the dog and cat the parotid derives its 

 nerve-supply from the glosso-pharyngeal through the small petrosal 

 and the otic ganglion, the fibers finally running into a branch of the 

 auriculo-temporal. 



The submaxillary gland is separated from the parotid by a pro- 

 cess of the deep cervical fascia. It is beneath the mylohyoid muscle, 

 is below the curve of the digastric muscle, and on the outside is 

 covered by the subcutaneous cervical muscle and skin. It is about one- 

 third the size of the parotid, and its duct of Wharton is about two 



