8 THE STRUCTURE AND FUNCTIONS 



becomes the immediate agent of absorption in certain morbid 

 processes. 



" Absorption,"* says Professor Miiller, " seems to depend on 

 an attraction, the nature of which is at present unknown, but 

 of which the very counterpart, as it were, takes place in secre- 

 tion; the fluids altered by the secreting action being impelled 

 towards the free surface only of the secreting membranes, 

 and then pressed onwards by the successive portions of fluid 

 secreted. In many organs, for instance in those invested 

 with mucous membranes absorption by the lymphatics and 

 secretion by the secreting organs, are going on at the same 

 time on the same surface." It appears, however, from what is 

 stated in the present chapter, and in the Trans. Roy. Soc. 

 Edin.f that Prof. Muller, and indeed all the physiologists hitherto, 

 have been in error in supposing the forces of secretion and ab- 

 sorption as of different and opposite tendencies the one attrac- 

 tive, the other repulsive. They are both attractive, absorption 

 being but the first stage in the process of secretion. Secretion, 

 in fact, differs from absorption, not physiologically, but morpho- 

 logically. 



What has been stated in the present paper explains also how, 

 in the mucous membranes, " absorption by lymphatics and secre- 

 tion 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 germinal membrane the 

 secreting epithelia are on its free surface ; the former are inter- 

 stitial cells the latter peripheral ; the former cast their contents 

 into the substance of the organism the latter into the surround- 

 ing medium. 



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

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



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

 creased quantity of blood circulates in the capillaries of the gut. 

 In consequence of this increased flow of blood, or from some 



* Miiller's Physiology, page 30. Baly's Translation. 



t Trans. Royal Society, Edin. 1842, '' On the Secreting Structure, and Laws of its 

 Function." 



