Chap. VII. 



OSTEOLOGICAL DIFFERENCES. 



263 



which deserve attentive consideration. The upper and anterior cavity 

 of the three into which the skull may be divided, is the one which is 

 so greatly modified; it is evidently much larger than in the Cochin 

 skull of the same size, and extends much further beyond the interorbital 

 septum, but laterally is less deep. Whether this cavity is entirely filled 

 by the brain, may be doubted. In the skull of the Cochin and of all 



Pig. 35.— Longitudinal sections of Skull, of natural size, viewed laterally. A. Polish Cock. 

 B. Cochin Cock, selected for comparison with the above from being of nearly the same size. 



ordinary fowls a strong internal ridge of bone separates the anterior from 

 the central cavity ; but this ridge is entirely absent in the Polish skull 

 here figured. The shape of the central cavity is circular in the Polish, and 

 lengthened in the Cochin skull. The shape of the posterior cavity, together 

 with the position, size, and number of the pores for the nerves, differ much 

 m these two skulls. A pit deeply penetrating the occipital bone of the 

 Cochin is entirely absent in this Polish skull, whilst in another specimen 

 it was well developed. In this second specimen the whole internal 

 surface of the posterior cavity likewise differs to a certain extent in 

 shape. I made sections of two other skulls,— namely, of a Polish fowl 

 with the protuberance singularly little developed, and of a Sultan in which 

 it was a little more developed ; and when these two skulls were placed be- 

 tween the two above figured (fig. 35), a perfect gradation in the configura- 

 tion of each part of the internal surface could be traced. In the Polish 

 skull, with a small protuberance, the ridge between the anterior and 

 middle cavities was present, but low; and in the Sultan this ridge was 

 replaced by a narrow furrow standing on a broad raised eminence. 



