MAMMALIA 643 



capsule, auditory capsule and optic capsule, as well as the jaws. The 

 walls of the olfactory capsule consist of the vomer, mesethmoid, 

 pterygoid, palatine, maxilla, premaxilla, lacrimal, nasal, and nasal 

 processes of frontal bones. The auditory capsule is enclosed in a por- 

 tion of the temporal bone. This bone is formed by fusion of the 

 squamous, petrous, and tympanic bones. 



The eat and other mammals have two sets of teeth, the milk or 

 deciduous set, and the permanent set. In the first set, the dental 

 formula for one-half of the mouth is incisors 3/3, canines 1/1, and 

 premolars 3/2. These teeth begin to appear when the kitten is two 

 weeks old and are complete at eight weeks. At the end of the fourth 

 month the milk incisors are being replaced by permanent teeth. The 

 formula for one-half of the mouth with permanent teeth is : incisors 

 3/3, canines 1/1, premolars 3/2, molars 1/1 or a total of thirty teeth. 

 Because of the different forms these teeth are said to be heterodont. 

 They develop like placoid scales from the epithelial lining of the 

 mouth, and each tooth consists of an outer, hard covering, the enamel, 

 under which is the dentine and then the pulp. The permanent set 

 in man includes 32 teeth and the formula for one-half of the set is 

 incisors 2/2, canines 1/1, premolars 2/2, molars 3/3. 



The vertebral column or backbone is composed of five groups of 

 vertebrae; seven cervical in the neck, thirteen thoracic in the chest, 

 seven lumbar in the small of the back, three sacral in the hip region, 

 and from four to twenty-six caudal in the tail. These vertebrae 

 articulate on each other. They are separated by intervertebral discs 

 of cartilage, except the fused sacral group. Intervertebral ligaments 

 serve to connect the vertebrae. The principal parts of the typical 

 vertebrae are : the body or centrum, neural arch over the central 

 canal, a spinous process or neutral spine projecting dorsally from the 

 arch, two transverse processes projecting laterally one on each side, 

 zygapophyses or articular processes, a pair projecting anteriorly and 

 a pair posteriorly to articulate with adjacent vertebrae. Articulating 

 laterally with the thoracic vertebrae are thirteen pairs of rihs which 



Fig. 348. — Muscles of the cat. a.s., occipitoscapularis (rhomioideus capitis) ; 

 cm., cleidomastoid ; ex. lonq. dig., extensor longus digitorum ; F. G. U., flexor carpi 

 ulnaris ; flex. long, dig., flexor longus digitorum ; flex. long, hal., flexor longus 

 hallucis ; F. P. D., flexor profundus digitorum; gastroc, gastrocnemius; int. ohliq., 

 internal oblique; L. S. V., levator scapulae ventralis ; P.A., pectoralis ; parot^, 

 parotid gland ; Pt, pronator teres ; spl, splenius ; sub^n., submaxillary gland ; T, 

 triceps brachii : trans., transverse abdominis. (From Stromsten, Davison's Mam- 

 malian Anatomy, published by The Blakiston Co.) 



