192 



DUCTLESS GLANDS 



are produced. Some of the mucous membrane of the small in- 

 testine was scraped off, treated with acid, and injected into the 

 ., blood. Immediately, pan- 



creatic juice flowed. The 



^.^mectl body ^^""^ ^^ thought to have 

 r(7^xj--^-\^--.Tpxtui'ta^ been effected by the stim- 

 ulation of the diojestive 



.partcthyK)i^S gl^^^^s by secretin which 



*J^- ---"fhyroxoL was probably formed from 



% V-^ -'.t'KyTriTXS ^1^ inactive hormone in the 



mucous membrane. 



The internal secretions 



llV^T* are of great importance in 



._.pancreoc» bringing about coordina- 



jspleen. ,. ,. 



' tion among the various 



• /-— -OCCirdnatlS organs. It is thought by 



'^ some investigators that 



Most of the ductless glands of man are indicated in i • i e •• 



their approximate positions. CVCry kind ot tlSSUC may 



give rise to individual sub- 

 stances or principles which pass directly into the blood, and affect 

 the general working or metabolism of the body. Not many studies 

 have been published ^concerning tissue secretion. To date, in- 

 vestigations have been confined largely to the hormones of the 

 ductless glands. 



It is difficult to secure the internal glandular secretions of human 

 beings in a pure state. Therefore, our knowledge concerning 

 them is based primarily on experimentation on lower animals, 

 chemical examination of the glands and their extracts, and of 

 the blood near the glands, observations of the effects resulting 

 from disturbances of the ductless glands, and effect of direct 

 injections of extracted or synthesized internal secretions. 



The thyroid. The thyroid is one of the ductless glands. It is 

 situated in the neck and consists of two divisions or lobes, one on 



