Chap. III.] GENERAL ANATOMY. 39 



The small intestine passes into an oval sac (sacculus rotundus), 

 with walls resembling Peyer's patches. Just beyond this there 

 is given off a very large dark thin-walled diverticulum (the 

 ccecum, Cce.), round which there passes a spiral constriction. 

 It ends blindly in a finger-like process (appendix vermiformis), 

 the walls of which are thicker, and again resemble Peyer's 

 patches. 



Just beyond the sacculus into which the small intestine passes, 

 and beyond the csecal appendage, is the commencement of the 

 large intestine, which seems at first sight to be a continuation of 

 the caecum. Soon, however, it narrows and becomes puckered 

 with lateral and median sacculations. Gradually the saccula- 

 tions of this anterior portion (colon, Co.) of the large intestine 

 become less marked, and it passes into the terminal smooth 

 portion (rectum, rm.) of the alimentary canal, which contains pill- 

 like balls of faeces. It passes from the right anterior corner of 

 the abdominal cavity backwards through the pelvic arch to open 

 externally by the anus, near which rectal glands are developed 

 on either side of the rectum. The relative lengths of the vari- 

 ous parts of the alimentary canal should be measured. The 

 total length is some fifteen or sixteen times the length of the 

 body. For the examination of its parts it must be turned over 

 in the ccelom. 



2. The Respiratory System. The roof of the mouth, which 

 forms also the floor of the nasal chambers, is transversely ridged. 

 This is continued backwards as the soft velum palati above which 

 the two nasal passages become confluent. These nasal passages 

 may be regarded as the air-track, the mouth as the food-track. 

 Note that the air-track is here dorsal. The food-track continues 

 as the oesophagus, the air-track as the trachea, through the glottis, 

 which is guarded by the tongue-like epiglottis in front arid the 

 cornicula laryngi behind. Note that here the air-track is 

 ventral, so that in the pharynx the air-track and the food-track 

 cross. 



Behind the glottis is the larynx or organ of voice (the brown 

 glandular mass on either side of and beneath which is the 

 thyroid gland). The air-track continues as the trachea, strength- 



