DEVELOPMENT OF HUMAN PHARYNX 375 



Thus to the embryologist falls the duty of contributing a respect- 

 able portion of the facts, while the character of his problems 

 gives him a peculiar interest in certain sides of the general inter- 

 pretations. 



In the group of the endocrine or 'internally secreting glands'- — 

 so-called — two things stand out strongly: (a) The close correla- 

 tion between them on the physiological side, showing particularly 

 in their pathological derangement, so that hypertrophy or 

 abnormal growth in the one is in some way correlated with 

 abnormal changes in other endocrine organs. The organs 

 thus particularly linked are^ thyreoid, hypophysis, suprarenal; 

 thyreoid, hypophysis, thymus, gonad; parathyreoid, thryoid; 

 parathyreoid, gonad (?); thymus, thyreoid; thymus, gonad, 

 lymphatic organs; thymus, suprarenal (?); suprarenal (medulla), 

 pancreas (islands of Langerhans ?); suprarenal (cortex), gonad; 

 suprarenal cortex and medulla; hypophysis, gonad; hypophysis, 

 thyreoid; pineal body, gonad, hypophysis. The evidence that 

 these structures are bonded by either a 'functional interdepend- 

 ence' or vicarious or reciprocal functioning is, it would seem, 

 very slight or lacking; the physiological characteristics that 

 they possess in common clearly lie deeper, (b) The second 

 peculiarity of the group of endocrine organs contrasts, it would 

 seem, with their common metabolic features and is at variance 

 with the rule that organs which may be grouped in a natural 

 physiological system also show a unity in development, so 

 that parallel embryologic systems exist. In the case of the 

 structures under consideration, the greatest diversity of origin 

 prevails; their characteristic parenchyma is from all the germ 

 layers and parts of the embryonic body regionally remote and 

 unrelated, while material of quite distinct sources may become 

 associated — as in the case of the hypophysis and suprarenal 

 body. Several of them come out of the embryonic pharynx 

 "or its immediate neighborhood — hypophysis, thyreoid, para- 



^ The writer makes no claim to first-hand information in this complicated 

 physiological field. The grouping here given is based mainly on Biedl: "Die 

 Innere Sekretion." My colleague, Dr. S. Simpson, kindly examined the above 

 list. 



