8 INTERNAL SECRETION 



agency of the internal secretions of various organs, more 

 particularly the liver. It is a question of expediency and one 

 which each physiologist will decide for himself, whether or not 

 these antitoxic processes the measures, that is, which are adopted 

 on the part of the organism to guard against auto-intoxication 

 should be included in the definition of the internal secretions, 

 while the antitoxic activity of the liver, where exogenic poisons 

 are concerned, is excluded from it. 



CLASSIFICATION. 



Having defined the field which the internal secretions cover, 

 the next step is to classify them. Berzelius divided the true 

 glandular secretions into recrementitial and excrementitial, and, up 

 to now, a similar distinction has been maintained in regard to 

 the internal secretions. As far as we can judge at present, the 

 process of internal secretion has a twofold aspect. In the first 

 place there is positive recrementitial secretion or production of 

 hormones. In the second, there is that activity of the organs 

 which is sometimes called negative secretion, which concerns 

 itself with the neutralization of materials circulating in the blood 

 which might otherwise impair the activity of other organs, or 

 even endanger the well-being of the entire organism. The latter 

 function is a parallel to the external secretion of the true excretory 

 organs, as the skin, the intestine, the lungs and the kidneys, by 

 whose agency the body is freed from useless and harmful 

 substances. 



But it is very obvious that there is an essential difference 

 between the two processes. The excretory organs are able to 

 expel undesirable material from the body, but in the case of the 

 internal secretory organs this method is impossible. In the 

 absence of any channel communicating with the exterior, the 

 substances which have been withdrawn from the blood must, 

 sooner or later, be returned to the blood. The organism as a 

 whole, therefore, can be relieved in only one of two ways. Either 

 the effete substances must be retained in the organ, or they must 

 be rendered innocuous before they are again returned to the blood. 



The former process comes into play chiefly in the management 

 of those waste materials which circulate in the blood as formed 

 elements. The adenoid or lymphatic tissue distributed over the 

 body, the bone-marrow, the spleen, and the liver are all organs 

 which, by a kind of filtering process, retain the broken-down 

 remains of old red and white corpuscles, remnants of tissue, traces 

 of pigment, &c., and in this way they free the blood of useless 

 morphological elements. The particles which have become fixed 

 then undergo secondary changes, after which they supply the 

 material for fresh organic activity ; thus, iron goes to build up the 

 red blood corpuscles, pigment to the preparation of bile. 



