190 CHARLES R. STOCKARD AND A. L. JOHNSON 



Wide differences again stand out when the distances from 

 the orifice of the auditory meatus to the anterior tip of the 

 superior dental alveolus (pi. 35, fie,'. 3, O-F) are arranged 

 in sequence based on the regular decrease in distances from 

 the meatus to the bregma. A comparison of text-figures 38 

 and 35 illustrates quite vividly the contrast between type 

 significant and insignificant measurements. The measure- 

 ments from the meatus to the tip of the superior dental 

 alveolus range from 200 mm down to only 57 mm, or as 

 3.5 :1. Text-figure 38, for this measurement, is the most widely 

 irregular in the series and shows no correlation whatever 

 with the meatus-bregma measurements. It indicates more 

 clearly than the other charts, however, the enormous devia- 

 tions in type characteristics which exist in these dog skulls 

 from many different breeds. 



The length of muzzle in the dog is the determining feature 

 in numerous types of skulls, and the nature and origin of 

 reductions in muzzle length is a problem of primary im- 

 portance in connection with the influences of modified internal 

 secretions on the growth and development of structural pat- 

 terns. We shall discuss these features more completely in 

 other parts of this report. 



Finally we may make a comparison between the measure- 

 ments of distance from the auditory meatus to bregma and 

 from the meatus to a more posterior point on the skull. 

 This may serve to indicate whether the posterior skull region 

 is as variable in length as we have found the anterior portions 

 to be. Measurements were made from the orifice of the 

 auditory meatus to the supraoccipital spine (pi. 35, fig. 3, 

 O-B). It should be recalled at this point that the skulls of 

 certain breeds show a pronounced occipital crest which has 

 at its posterior end the supraoccipital spine, while other 

 dog skulls are quite tlat with a poorly expressed spine. The 

 flat topped cranium is as a rule wider than the crested type, 

 yet to some extent a prominent crest and spine no doubt 

 exaggerate and vitiate the relative distances from the meatus 



