Chap, xvii.] OF SECRETION AND EXCRETION IN GENERAL. 261 



absorbs any, secrete with much greater activity, and thus com- 

 pensate in a large measure for the inaction of the pancreatic 

 gland.i 



These valuable researches, which put beyond doubt the 

 fact of the intimate solidarity between the spleen and the 

 pancreas, show how very complex the phenomenon of secretion 

 can be. The cells of the spleen do not fabricate pancreatic 

 ferment, and there is no trace of this ferment in the blood ; never- 

 theless the function of the pancreas is abolished Tphen the spleen 

 is extirpated. In order that the pancreatic glands may elaborate 

 pancreatine at the expense of the albuminoidal substances, or of 

 certain of these substances, it is needful, previciusly, for the 

 materials, absorbed by election into the pancreatic gland, to 

 undergo, in the cells of the spleen, a first modification, a first 

 process, the nature of which is still unJmown. 



But who can say how many of these physiological correlations 

 are still unknown, and how fertile the study of the other closed 

 glands may be, undertaken from that point of view ? 



The glands with excretory conduit must be considered as folds, 

 as diverticules of the cutaneous or mucous teguments. The 

 labour of specialisation bears especially on the epithelium or the 

 epidermis of the tegumentary membrane ; the mode of nutrition 

 of this epithelium is modified, and its cells acquire the faculty 

 of elaborating at the expense of the blood, here saliva, there 

 gastric or pancreatic juice ; at one point bile, elsewhere spermatic 

 liquid, and so on. 



The humours secreted have all two general characteristics : — 



1. None of the humours is living; none is endowed with the 

 property of continuous renovation which we have signalised in 

 the plasmas. Their water is in great part free ; it is not a 

 constituent water, and it is charged with salts directly dis- 

 solved. 



2. All these humours contain one or more quaternary principles, 



^ A. Her?en, Sulla Digestione dell' Albumina Effettuata dal Succo Pancre^ 

 atico e sulla Funzione della Milza, 



