SKULL AND BRAIN IN MAN. 257 



b. The cervi co-cephalic angle is the angle made by the axis 

 of the spine with the axis of the head. This angle does not 

 exist in the fish and amphibian, in which the axis of the 

 head and spine forms a continuous line. In reptiles, birds, 

 and mammals, this angle is more or less - — ^»»**™—- 



marked, but in none of them does it 

 reach a right angle. In the different 

 mammals the an<j;le varies with the 

 species. In man alone is the cervico- 

 cophalic angle a right angle. Fig. 15. 



r Tn i.i-in flio neciin'tol fnmmon Diagrammatic outline of the 



c. in man ine occipital ioiamen, cranio _ sl , inal axisof a 1isll) ,,, ., 



1 . i P n , 1 -i reptile, bird, or mammal, and of 



and the upper surfaces of the nasal a man. 



foss?e lie in a horizontal plane, the mesial line of which is 



the cephalic axis. 



In the animal (mammal) again, the occipital foramen and 

 floor of the nose lie in two planes at an angle to one another. 

 The palatal plane, in which the cephalic axis lies, is inclined 

 downwards at the cervico-cephalic angle. The occipital plane 

 is inclined upwards from the palatal at an angle which 

 increases in the descending order of the mammalian series. 



d. In man the cribriform plate, and the line of osseous 

 attachment of the tentorium, lie in a plane parallel to the 

 palato-occipital, and therefore horizontal. 



In the animal this plane is divided, so that its cribriform 

 and tentorial portions are elevated at an angle which increases 

 with the descent of the mammalian series. 



d. The squamous plate of the occipital bone, and the plane 

 of the occipital foramen are inclined to one another in man, 

 at ;ui angle which increases with the developmenl of the 

 cerebellum. This angle, which may be termed the squamo- 

 occipital, increases ra the descending scries of the mammals. 



r. The slope of the basilar process forms, with the line 

 of the cephalic axis, an angle which diminishes as we 

 descend the series. This angle the occipito-basilar angle — 



