GENETIC TYPE AND THE ENDOCRINES 287 



opening faces directly ventral, a strikingly different place- 

 ment from the other two. It may be recalled that this foramen 

 is quite similarly altered in its position in the human achondro- 

 plasia skull, as shown in plate 51. The location of the two 

 basicranial cartilages is clearly seen in all three skulls. 

 The segments of the basicranium are shorter and wider in 

 the complete bulldog typed skull than in the other two. 



At 2 months of age, the hybrid bulldog skull again shows 

 the presence of an enormous hypophyseal foramen in the 

 posterior segment of the basisphenoid (fig. 5). The pharyn- 

 geal epithelium still retains its embryonic connection with 

 the arrested glandular pituitary through this huge foramen. 

 Such foramina, along with other evidence on the histology 

 of the pituitary which is to be presented, make it apparent 

 that considerable arrest in hypophyseal development is as- 

 sociated with both acromegalic giant and achondroplasic bull- 

 dog types. The embryonic arrests in these breeds are sig- 

 nificantly involved in adult abnormalities of the pituitary. 



The two posterior segments of the basicranium of the 

 complete bulldog skull (fig. 6) are drawn more closely to- 

 gether than in the other two although all three dogs from 

 which the skulls were taken were of about the same age. 

 The lateral parts of the epiphyseal space in the bulldog skull 

 are almost obliterated through an early ankylosis of the bones 

 due to chondrodystrophy of the growth cartilage. 



The anterior part of the palate in the bulldog skull has 

 been dissected away to expose the bone underlying the small 

 erupted milk teeth. There are four deciduous incisors on the 

 right side instead of the usual three, and this dissection was 

 made to find whether an accessory permanent tooth was also 

 present. The immature permanent incisor may be seen crowd- 

 ed into a posterior position between the median and the 

 middle right incisor tooth germs. Numerous anomalies of 

 this kind, which are probably associated with an unstable 

 mutational type, are frequently present in these highly modi- 

 fied skulls. 



