7i6 



MAMMALIA. 



almost obliterated. The thoracic cavity is separated from 

 the abdominal cavity by a partly muscular diaphragm, 

 which is supplied by two phrenic nerves, arising from the 

 fourth cervical spinal nerves. By its contraction the 

 diaphragm alters the size of the thoracic cavity, and thus 



olfj 



cb 



\ 



\ 



stnx 



\ 



epg 



pmx 



s.L 



FIG. 392. Vertical section through rabbit's head. From a section, 

 with help from Parker's Zootomy and Krause. 



pmx., Premaxillawith incisors ; nt.e., part ofmesethmoid partition ; 

 t.b., maxillary turbinals ; e.t., ethmoidal turbinal ; m.e., part 

 of mesethmoid ; olf.L, olfactory lobe of cerebrum ; ps., pre- 

 sphenoid; c.c., position of corpus callosum ; bs., basisphenoid 

 with depression for pituitary body ; cb., cerebellum ; b.o., basi- 

 occipital ; s.c., spinal cord ; n.#., nasal passage ',-., gullet ; tr. t 

 trachea; epg., epiglottis; smx., submaxillary salivary gland; 

 s.L, sublingual salivary gland; 7 1 ., tongue; //., transverse 

 portion of palatine ; win., anterior end of mandible. 



shares in the mechanism of respiration. At the top of 

 the trachea lies the complex larynx, the seat of the voice 

 in Mammals. 



Anteriorly the larynx is supported on its sides and beneath by the 

 thyroid cartilage ; behind this lies the ring-like cricoid ; dorsally to the 

 cricoid are two small triangular arytenoids. 



