234 VERTEBRATE ZOOLOGY 



The infraorbital gland lies on the ventral wall of the orbit. It 

 will be seen when the orbit is dissected. Its duct opens into the 

 mouth just back of the upper molar. 



Exercise 25. Draw an outline of the head and show the position of 

 the salivary glands. 



Cut away the lips and expose the teeth. Shut the jaws and 

 observe the relation of the teeth of the lower jaw to those of the 

 upper. The dental formula of the cat is the following : incisors f , 

 canines \ , premolars f , molars \ . The milk teeth of the young 

 cat lack the molars. 



Exercise 26. Draw a front and also a side view of the closed mouth, 

 with outlines of the teeth. 



Cut through the muscles on each side of the head from the angle 

 of the mouth to the end of the jaw. Disarticulate the lower jaw, 

 first cutting it with bone forceps, if necessary, and turn it down, 

 exposing the cavities of the mouth and pharynx. The two cavities 

 form a single space extending from the lips to the beginning 

 of the oesophagus. The mouth is much the larger of the two spaces 

 and extends from the lips to the free edge of the soft palate ; the 

 pharynx lies between this point and the oesophagus, and is the 

 space in which the path of the respiratory air from the nostrils tc 

 the lungs crosses that of the food from the mouth to the stomach. 



The mouth cavity itself is made up of two regions : the vesti- 

 bule, that part between the lips and cheeks and the jaws and 

 teeth; and the mouth proper, or that part between the teeth 

 and the soft palate. A median fold called the frenulum unites 

 the upper lip with the jaw. The lower lip and the lower jaw are 

 also united by frenula, not only in the median plane but also on 

 each side, just back of the canine teeth. 



The roof of the mouth is formed by the hard and the soft palate. 

 The hard palate, which forms the anterior portion, is characterized 

 by a number of curved, transverse ridges, between which are rows 

 of papillae. Between the anterior ridge and the incisor teeth is a 

 large median papilla; on each side of this is the opening of the 

 duct leading to the organ of Jacobson, a small sensory organ of 

 uncertain function, lying on the floor of the nasal cavity. 



