HISTORICAL AND INTRODUCTORY 3 



the 1 8th century and was discovered by Neuburger) ascribed the 

 changes which occur after removal of the sexual organs and in 

 certain other conditions, to a deficiency or superfluity of the 

 glandular secretions. The existence of normal and pathological 

 secretions was known, but no account was taken of substances 

 which are formed by all the organs, including those which are 

 not in the first instance secretary organs, and which contribute 

 something to the composition of the plasma. 



An important step forward was marked by Johannes Miiller 

 in his text-book of physiology. He drew a sharp distinction 

 between secretion the formation of a specific chemical substance 

 by the organ and excretion the change of place of the already 

 formed substance. He recognized secretory cells, secretory mem- 

 branes, and secretory glands. Among the latter he included 

 those organs which are known as the vascular ganglia or blood 

 glands, namely : the spleen, the thyroid, the suprarenals, the 

 thymus, and the placenta. 



Miiller believed that these ductless glands " exert a plastic 

 influence upon the juices which are within them, which circulate 

 through them, and which are carried from them by the general 

 circulation. Unlike the other glands, however, they exercise no 

 external influence." 



It was Professor A. A. Berthold, of Gottingen, who, in 1849, 

 first demonstrated by means of experiment the nature of the 

 activity of a true ductless gland ; that is to say, he showed the 

 influence which an organ through which the blood-stream circu- 

 lates, can exert upon the composition of the blood and thus upon 

 the entire organism. He removed the testicle from cocks and 

 grafted it upon another part of the body; and he found that " the 

 animals remained male in regard to voice, reproductive instinct, 

 fighting spirit, and growth of comb and wattles." He concluded 

 that " the consensus is maintained by the productive influence 

 of the testicle ; that is to say, by its effect upon the blood and, 

 through the blood, upon the organism." The honour of having 

 first proved the existence of an " internal secretion ' and of 

 having recognized its significance, belongs undoubtedly to 

 Berthold. 



Berthold's discovery, how r ever, received no recognition in 

 his own day. The physiologist, Rudolf Wagner, was unable to 

 confirm the experiments, and Berthold was probably unknown in 

 general circles. Claude Bernard, in 1855, is generally credited with 

 having been the first to give expression to the doctrine of an 

 internal secretion. He maintained that, not only the glands by 

 their secretory processes secretion externe by means of which 

 substances are withdrawn from the blood, but that every organ 

 of the body, by a process of secretion interne whereby it yields its 

 products up to the blood, determines the composition of the blood 

 and can, under certain conditions, modify and even change it. 



