GENETIC TYPE AND THE ENDOCRINES 



381 



between 54 and 41. This indicates that the general shape and 

 proportions of the mandible are very uniform in the normal 

 group. The range in values is steeper and wider in the B, 

 C and D groups, and the tendency is toward higher mandibular 

 indices. The indices for almost all the forty-nine mandibles 

 in the normal group are about 50 or lower, while the majority 

 in each of the three groups with minor malocclusions are 

 higher than 50 and in a few specimens reach to above 70. 

 In spite of these differences for the indices in the B, C 

 and D groups, more than half the specimens lie within the 

 range of the normal indices. These facts suggest very clearly 

 that the mandibnlar index is not so directly concerned in 



70 



80 

 70 

 (,0 

 SO 



Text-figure 76. Relation of dental occlusion to mandibular index in 184 skulls 

 divided into groups as indicated in text-figure 72. 



dental malocclusion as is the palatal index represented in 

 text-figure 75. 



The mandibular indices in group E, those specimens with 

 complete malocclusion, range from above 80 down to 52. Thus 

 these extreme cases are also within the upper limits of the 

 normal range although they do not show indices with values 

 so low as those in the first four groups. These prognathous 

 mandibles have an average index well above the normal, 

 yet they do show, as do the palatal index relations for the 

 same skulls, an overlapping with the values for the normal 

 group. Therefore, we can conclude that modifications in the 

 palate and the maxilla are more largely responsible for 

 dental malocclusion in the dog than are changes in width- 

 length relations of the mandible. In bulldog malocclnsions, 



