GENETIC TYPE AND THE ENDOCRINES 113 



The last two skeletons, the fifth and sixth in the group, 

 are considered to be homozygous or pure for achondroplasia 

 shortness, ss. In spite of the same genotype for this defect, 

 there is considerable difference between the degrees of de- 

 formity shown in the Uvo leg skeletons. The scapula of the 

 fifth specimen is much narrower than the scapula of the 

 heterozygous hound bone to the left. The humerus is longer, 

 slenderer and less deformed in the fifth skeleton than in the 

 sixth. The foreleg bones of the two differ in a similar way 

 and in the fifth leg the end of the ulna extends as low as 

 the radius, but does not do so in the sixth. The foot is rotated 

 in both, but can be more widely abducted in the sixth specimen 

 than in the fifth. The fifth skeleton shows its deformity on 

 what is interpreted as almost pure typed shepherd bone, while 

 the last specimen shows an accentuation of the same de- 

 formities on pure hound typed bone. These two bone consti- 

 tutions cannot be considered as extremely different in type, 

 but they nevertheless do give rather clearly differentiated 

 responses to the genie influences for the achondroplasia growth 

 defect of the leg. 



Leg skeletons of tin' F., bassethound-Saluki. Among the 

 second generation hybrids from the cross between the basset- 

 hound and Saluki, differences in slenderness of leg without 

 regard to differences or similarities in leg length are con- 

 stantly observed. These differences in slenderness depend 

 ui)on whether the animal has developed bone more nearly 

 that of the Saluki or that of the hound. The bone constitution 

 in this case, as in the cross considered above, influences the 

 degree of expression in the achondroplasia deformity. 



The skeletons of the right front legs from six litter mate 

 F 2 bassethound-Saluki hybrids are shown in plate 25. Begin- 

 ning at the left they are as follows: one recessive long slender 

 leg, two heterozygous si short legs, and three homozygous 

 ss more fully shortened legs. The animals from which these 

 leg skeletons were taken are shown in plate 10 (p. 73). Figure 

 5 (pi. 10) is F L , 1441<5 whose leg skeleton is fourth in plate 

 25 and who is again shown in plate 12 (p. 77) as homozygous 



