476 



MANUAL OF ELEMENTARY ZOOLOGY 



(Fig. 319) ; there is no centrale in the wrist ; the bones of the 

 adult skull show considerable fusions, there being a single "occipital 

 bone" composed of basioccipital, exoccipitals, supraoccipital, and inter- 

 parietal, a "sphenoid bone " composed of basisphenoid, alisphenoids, 

 presphenoid, orbitosphenoids, and pterygoids, an "ethmoid bone" 

 composed of mesethmoid, ectethmoids, turbinals and vomer, and a 

 "temporal bone" composed of squamosal, tympanic, periotic, tym- 

 panohyal, and stylohyal ; small, irregular, additional bones (Wormian 

 bones) may be found in the course of the sutures of the roof of the 

 skull ; the pancreatic duct joins the bile duct near the entry of the 

 latter into the duodenum ; the vermiform appendix is a good deal 



ILEOCOLIC ARTERY 



ILIAC BRANCH 



Fro. 356.— The ccecum and neighbouring structures in man. From 



Cunningham. 



1, Ileum ; j, colon ; 3, csecum ; 4, appendix. 



smaller and the caecum very much smaller ; the left superior vena cava 

 (or innominate vein) joins that of the right side before the latter enters 

 the heart, forming thus a single superior vena cava ; the external and 

 internal iliac veins of each side join to form a common iliac; the 

 fibres which form the depressor nerve of the rabbit are included in the 

 main vagus nerve ; there is a single pair of mamma-, which are on the 

 thorax; the uterus is a single, median structure; the testes descend 

 into an external scrotum ; a seminal vesicle opens into the hinder end 

 of each vas deferens; and the third eyelid is represented only by a 

 slight, semilunar fold of membrane, the///'<-a semilunaris. 



