GENETIC TYPE AND THE ENDOCEINES 377 



groups, B with individual malplaced teeth, C with incisors 

 meeting- end to end, and D with the mandibular incisors 

 anterior to the upper, all range much higher in total skull 

 index than the group with normal occlusion. Practically every 

 skull in these three groups is shorter than the average for 

 the A group, but in the lower indices a number overlap or 

 fall within the range of the highest indices in the normal 

 group. The twenty-nine skulls in the completely undershot 

 E group are all higher in index than any of those with 

 normal occlusion. This would indicate that fully expressed 



so — 

 70 — I 



60— I 

 so—\ 



: J 



A B C D E F G 



Text-figure 72. Relation of dental occlusion to total skull index in 184 skulls 

 divided into groups as follows: A, forty-nine skulls with normal occlusion; B, 

 seventeen skulls with malocclusion of a few individual teeth; C, seventeen skulls 

 with incisors meeting end to end; D, sixty skulls with mandibular incisors in 

 front of maxillary incisors (undershot) ; E, twenty-nine skulls with entire 

 mandibular series anterior to maxillary series (undershot) ; F, five skulls with 

 mandibular incisors or molars (or both) posterior to corresponding maxillary 

 teeth (overshot) ; G, seven skulls with poor, irregular occlusion. 



prognathism of the mandible is confined to short skulls of 

 high index; in addition, group D shows that about 66 per cent 

 of the skulls with but slight mandibular prognathism are also 

 shorter than any in the normal group. In group G the seven 

 skulls with deformed and irregular occlusion are all of higher 

 index, that is, shorter than the normal group. 



On the basis of total skull index, therefore, it is strongly 

 indicated that normal dental occlusion in the dog is confined 

 to the long typed primitive skull, while the modified short 



