CLASS MAMMALIA. MAMMALS 



471 



ble bladder (Fig. 343). At intervals the 

 muscular walls of the bladder are voluntarily 

 contracted, forcing the urine out through 

 the urethra. In the male the urethra passes 

 through the penis. 



Nervous system 



The cat possesses a brain, cranial nerves, 

 spinal cord, spinal nerves, and an autonomic 

 nervous system. 



f Dorsal aorta 



i Posterior vena cava 

 sr — j- Adrenal gland 

 ^ — *-RenaI artery 



■ y^ ) ■' Renal vein 

 .^^^Kidney 

 *-Ureter- 



Ostium 



Oviduct 



Ovary 



Horn of uterus 



Large intestine 



Bladder 



Vas deferens 



Prostate gland 

 Urethra 



Testis 



Epididymis-3i]l]^^ 



MALE 



Bulbourethral gland 



Scrotal sac 



Anus — — ' 



FEMALE 



Figure 343. Urogenital organs of the domestic cat, in ventral view. This illustration shows 

 that the urinary and reproductive organs of mammals are closely associated. 



The brain, as in other mammals (Fig. 

 344), differs from that of the lower verte- 

 brates in the large size of the cerebral 

 hemispheres and cerebellum. The cerebral 

 hemispheres are slightly marked by depres- 

 sions or sulci, which divide the surface into 

 lobes or convolutions not present in the 

 pigeon. This increase in cerebral tissue is 

 doubtless correlated with the greater intel- 

 ligence of the cat. The olfactory lobes are 

 very large and club-shaped. The optic lobes 

 are each divided by a transverse furrow into 

 two. The whole surface of the cerebellum is 

 thrown into numerous folds. Its high degree 

 of development is probably related to the 

 excellent muscular coordination in the cat, 

 which enables it to turn in the air and make 

 a "four-point landing" when dropped. 



There are 12 pairs of cranial nerves from 

 the brain, and from the nerve cord a pair of 



spinal nerves emerges between successive 

 vertebrae. 



Sense organs 



The organs of smell, taste, sight, and hear- 

 ing in the cat are ver)' similar to those of 

 man in location and function (see Chap. 

 33). The eye of a cat has a pupil which 

 varies in size and shape, depending on the 

 amount of light striking the iris. The metal- 

 lic luster which makes the eyes of cats 

 "shine" at night is due to light-reflecting 

 cr}^stals in part of the eye. The large outer 

 ear (Fig. 396) serves to collect sound waves; 

 the middle ear transmits the vibrations of 

 the tympanic membrane or eardrum by 

 means of three auditory bones (malleus, 

 incus, stapes), which extend across the tym- 

 panic cavity to the inner ear. This is un 



