21 6 HEREDITY AND EUGENICS 



thjToid one thinks and acts more quickly. One 

 milligram of th3'roxin is found to increase the rate of 

 metabolism 2 per cent. Cretin babies fed on th^-roid 

 undergo a remarkable mental and physical transforma- 

 tion to normal human beings. But the}^ must be fed 

 on it all their lives, or they relapse into their former 

 condition, because they are incapable of producing 

 the secretion themselves. More recently Keith (1922) 

 has elaborated his views on this subject in an extremely 

 interesting way, discussing such subjects as the 

 Neanderthal skull, acromegaly, dwarfism, and many 

 other anatomical alterations from the point of view 

 of hormone control. 



Seligman (1904) has described the frequent oc- 

 currence of " cretins " in Dexter Kerry cattle. The 

 breed appears to have originated, at Kerry at least, 

 as earh^ as the middle of the eighteenth centur3^ 

 One of its most striking features is the very short 

 legs, which suggest a condition of h^'pothyroidism. 

 In one herd fourteen cretins were produced among 

 fift^^-five calves in seven years. Another herd pro- 

 duced five cretins among tw^ent\'-seven calves in three 

 3^ears. These " bull-dog monsters " are non- viable, 

 and abnormal in man}^ respects. Their chief 

 peculiarities are their short trunk and extremely 

 dwarfed limbs (humerus onl}^ 1 3 millimetres in length), 

 the extreme brachycephaly of the head with its 

 rounded forehead bulging over the ver}' depressed 

 nose and upper jaw, while the lower jaw is normally 

 developed. There is always a gap in the abdominal 

 wall through which the internal organs protrude. 

 The palate is cleft, the tongue long and protruding, 

 while the thyroid is irregularly developed, and shows 

 the same histological peculiarities as the thyroid of 

 cretin children. It w^as probably devoid of proper 

 secretion, as the extract of such glands produced little 

 or no fall in blood pressure when injected intravenously. 



