468 



COLLEGE ZOOLOGY 



dominal viscera. The cat has facial muscles 

 which make possible a small degree of ex- 

 pression of emotional states. It is said, 

 however, that man is the only animal that 

 laughs. 



See Chapter 31 for further information on 

 the mammalian muscular system and its 

 functions. 



Digestive system 



The mouth cavity (Fig. 341), on the an- 

 terior portion of the roof, bears a series of 

 transverse ridges which help in holding the 

 food. That part of the roof which has a bone 

 foundation is known as the hard palate. 

 Posterior to this is a fleshy flap, the soft 



palate, which separates the mouth from the 

 pharynx. At the sides of the posterior part 

 of the soft palate are a pair of small reddish 

 masses of lymphoid tissue called the tonsils. 

 The tongue is attached to the floor of the 

 mouth. It bears a number of taste papillae 

 on the upper surface, which contain micro- 

 scopic taste buds. The two orifices of the 

 auditory (Eustachian) tubes, and the two 

 openings of the nasopalatine canals, which 

 connect the nasal and mouth cavities, are 

 situated in the roof of the mouth behind 

 and above the soft palate. There are 4 pairs 

 of salivary glands: (1) the parotids, below 

 the ears; (2) the infraorbitals, below the 

 eyes; (3) the submaxillaries, behind the 

 lower jaws; and (4) the sublinguals, next to 



Externa 

 nares 

 Thyroid 

 gland 



Nerve (spinal) cord i — Posterior vena cave 



Urinary bladder 



-Vas deferens 



Prostate gland 



I Urethra 



I — Rectum 

 -Penis 

 rTestis 



Right ventricle — \ 

 Thoracic cavity ^ 



Figure 341. The internal structure of the domestic cat. 



