GENETIC TYPE AND THE ENDOCRINES 155 



and nasal length, from the nasion to the anterior end of the 

 sagittal suture of the nasal bones, line I-J. A series of 

 transverse measurements was also taken. Beginning an- 

 teriorly, they are : line A, incisal alveolus width, the straight 

 distance between the alveoli of the right and left third 

 incisors ; B, internasal width, the distance between the antero- 

 lateral spines of the two nasal bones; C, canine alveolus 

 width, the distance between the posterior alveolar borders of 

 the canines; D, interorbital width; E, least frontal width, the 

 narrowest line of the frontal region; F, the zygomatic ividth; 

 and Gr, the cranial width. 



The measurements taken on other aspects of the skull may 

 be readily seen and understood by an examination of the 

 figures and accompanying explanations. We need only com- 

 ment on some of the measurements shown in the lateral view 

 (fig. 3). The orifice (0) of the external meatus proved to be 

 the most satisfactorily fixed point from which to measure 

 distances to other points on the skull. The head-spanner was 

 used to determine straight distances between this point and 

 the posterior border of the occipital condyle, the supraoccip- 

 ital spine, the bregma, the nasion, the anterior end of the 

 internasal suture and the most anterior limit of the superior 

 dental alveolus. We shall find that certain measurements 

 are almost consistently of the same length in all skull types, 

 while others show great differences and are of primary im- 

 portance in the differentiation of types. 



The control shepherd dog skull presents the measurements 

 shown in the second column of table 1 (p. 208) of pure breed 

 skull dimensions ; the averages, probable errors and standard 

 deviations are indicated. The length of skull base averages 

 19.27 cm with a standard deviation of 10.5 mm. The zygomatic 

 width is 10.8 cm, giving a total skull index of 56, which means, 

 of course, that the skull is very long and narrow. The cranial 

 index is 51. A further study of the table will bring out 

 the dimensions of this skull in reference to the points and 

 lines illustrated in the diagrams of measurements (pi. 35). 

 This control skull as such is more fully appreciated as we 

 proceed with the considerations of the various head types. 



