Allen: The Thyroid Gland and Hypophysis 



421 



DIAGRAMS TO SHOW HUMAN BODILY PROPORTIONS AT DIFFERENT STAGES CF 

 DEVELOPMENT FROM INFANCY TO MATURITY 



Illustration from C. B. Davenport (in Gcn2tic3 Vol. 2, page 350). (Fig 19.) 



the under functioning of the hypophy- 

 sis. This probably produces an under 

 functioning of the thyroid gland to 

 which the retardation in development 

 would appear to be more directly due. 

 Nevertheless the thyroid gland would 

 seem in these conditions to function 

 sulificiently to prevent the appearance 

 of myxoedema seen in the cretin. 

 In the latter cases the thyroid gland 

 has been deeply diseased in childhood, 

 not only involving a retardation in the 

 development of the structural features 

 and bodily proportions of maturity, 

 but resulting in features of myxoedema 

 as outlined above. The infantile pro- 

 portions seen in ateliosis and cretinism 

 involve a relative shortness of the 

 limbs. This is quite in line with the 

 very slight development of the limbs 

 of tadpoles deprived of the thyroid 

 gland, the pituitary gland or of both. 

 It is needless to say that here in the 

 tadpole we are also dealing with the 

 maintenance of infantile tadpole char- 

 acteristics. The similarity between 

 these features in man and in the tad- 



pole is more than a mere coincidence, 

 it is in each case due to a retardation 

 in bodily development. 



These statements are made with 

 the full recognition that they are partly 

 based upon debatable data, but in the 

 hope that they may lead to more accu- 

 rate observations along these lines. 



Achondroplasic dwarfs constitute a 

 class quite different from the above. 

 In them the trunk is little below normal 

 size but the head is usually very large 

 and the limbs extremely short. This 

 differs from cretinism chiefly in the 

 fact that there are no evidences of 

 myxoedema and in the large size of 

 the head, accompanied by hydro- 

 cephalus. The shortness of the limbs is 

 also more marked than in cretinism, 

 and intelligence is more nearly normal, 

 often quite so. This condition mani- 

 fests itself very early, usually in foetal 

 life as shown in the difficulty of labor at 

 birth. The cause of the condition is 

 very obscure but may well be due to 

 some abnormality of the thyroid or 

 pituitary glands of either the foetus or 



