398 ANATOMICAL AND TATIIOLOGICAL OBSEKVATIONS. 



Soc. Edin., * that Professor ]\f tiller, and indeed all the physio- 

 logists liitherto, have been in error in supposing the forces of 

 secretion and absorption as of different and opposite tendencies 

 — the one attractive, the other repulsive. Tliey are both 

 attractive, absorption being bvit the first stage in the process 

 of secretion. Secretion, in fact, differs from absorption, not 

 physiologically, but morphologically. 



What has been stated in the present paper explains also 

 how, in the mucous membranes, " absorption by lymphatics 

 and secretion by secreting organs are going on at the same 

 time on the same surface." There is no physiological mystery 

 in this. It depends on a morphological circumstance. The 

 absorbing chyle-cells are on the attached surface of the ger- 

 minal membrane — the secreting epithelia are on its free sur- 

 face ; the former are interstitial cells — the latter peripheral ; 

 the former cast their contents into the substance of the 

 organism — the latter into the surrounding medium. 



The primitive cell, then, is primarily an organ of specific 

 absorption, and secondarily of nutrition, growth, and secretion. 



As the chyme begins to pass along the small intestine, an 

 increased quantity of blood circulates in the capillaries of the 

 gut. In consequence of this increased flow of blood, or from 

 some other cause with which I am not yet acquainted, the 

 internal surface of the gut throws off its epithelium, which is 

 intermixed with the chyme in the cavity of the gut. The 

 cast-off epithelium is of two kinds — that which covers the 

 viUi, and which, from the duty it performs, may be named 

 protective epithelium, and that which lines the follicles, and 

 is endowed with secreting functions. The same action, then, 

 which, in removing the protective epithelia from the villi, 

 prepares the latter for their peculiar function of absorption, 

 throws out the secreting epithelia from the follicles, and thus 



* Trans. Royal Society, Edin. 1842, " Oii the Secreting Structure, ami 

 Laws of its Function." See also No. XXV. of this vohime. 



