612 JOHN D. KERN AN, JR. 



That of the occipital vertebra is small and shows no indepen- 

 dence of the costal element. It will be noted that this transverse 

 process, although in close contact with the costal bar, has not 

 yet formed a cartilaginous union with it (fig. 4, 6). This would 

 indicate that the costal and transverse processes of the occipital 

 vertebra take only a minor part in the formation of the lamina 

 alaris and paracondyloid processes. The second vertebra shows 

 an independent costal element which is drawn out caudad to 

 form the paracondyloid process. From its tip there passes to 

 the basioccipital that bar of cartilage already described as a rib 

 process. It is because of the connection of the paracondyloi-d 

 process to the basioccipital and occipital wing craniad and laterad 

 to the hypoglassal canal that it is interpreted as the rib process 

 of the second occipital vertebra. The most cranial vertebra 

 helping to form the basioccipital shows no free costal element. 

 The costal bar is prolonged upward on the occipital wing as a 

 ridge which represents, as already said, the inferior nuchal line 

 of the adult bone. 



That the occipital region of mammals is made up of a number 

 of vertebrae, all authors agree. The exact number has not been 

 definitely decided. Froriep ('86) found four in calf embryos. 

 Mead states the number as being three. 



As far as this present embryo offers any evidence on this point 

 at all, the number would appear to be three, that number of 

 transverse processes and ribs being indicated. 



Levi analyzed the human occipital region as follows: The 

 condyles he considered to represent the ununited body of the 

 occipital vertebra; the area between, reaching craniad to the 

 primitive break in the basal plate, he considered as the result of 

 the fusion of the body elements of the unsegmented vertebrae. 

 The paracondyloid process he called the tip of the arch of the 

 occipital vertebra; and the cartilage craniad to the hypoglossal 

 foramen, the fused neural arches of the unsegmented vertebrae. 

 He did not account for the cartilage bordering the foramen 

 magnum dorsal to the condyles. 



Macklin considered that the body element of the occipital 

 vertebra also helped form the area between the condyles border- 



