BOOK X 



THE FUNCTIONS OF THE DUCTLESS GLANDS 



CHAPTER LIX 

 INTERNAL SECRETIONS 



THE metabolism is greatly affected by what are known as the 

 i4 internal secretions." In certain glands there is elaborated material 

 which, instead of being discharged from the glands by a system of 

 ducts as an " external " secretion, passes from the gland cells into 

 the blood or lymph as an " internal secretion.'' Such may come 

 from glands which have no system of ducts e.g., the thyroid, supra- 

 renal or they may come from glands which are also provided with 

 a system of ducts e.g., pancreas, testes and have thez-efore both an 

 " external " and an " internal " secretion. 



Of late, researches have been extremely prolific in this branch of 

 physiology. So much is controversial that it is only possible to 

 indicate what appear to be the characteristic functions of each gland; 

 even these cannot be stated in a dogmatic manner. 



With the evolution of the multicellular organism there takes place 

 a differentiation of organs corresponding to a division of labour, and 

 an intenvorking of these organs is established. It is hard to say, 

 then, what are all the functions of any one organ, since an organ, in 

 performing these, not only fulfils its own life, but aids the functions, 

 growth, and nutrition of the other organs of the body. Thus, the 

 blood carries the heat developed in one part from that part to another, 

 an 1 thereby affects the working of ths body; it carries the hormones 

 " gastrin " and '' secretin," which provoke secretion of digestive juices; 

 it carries urea from the liver, where it is formed, to the kidney, where 

 it excites that organ to secretion. The muscles yield carbonic acid 

 and other acids, which, going to the respiratory centre, control the 

 respiration. The action of the secretions we are considering form 

 part of this inter working system, and the ke3aiote of their action is 

 their interdependence on one another. 



The whole body is bathed internally with tissue fluid or lymph, 

 and it is necessary that this fluid colloidal complex contain o;- 

 have linked to it various salts in proper proportions, also a 

 number of internal secretions. The diminution or excess of any 



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