ON THE INTESTINAL VILLI. 397 



primitive cell absorbs from the blood in the capillaries the 

 matters necessary to enable it to form, in one set of instances, 

 nerve, muscle, bone, if nutrition be its function ; milk, bile, 

 urine, in another set of instances, if secretion be the duty 

 assigned to it. The only difference between the two functions 

 being, that in the first, the cell dissolves and disappears 

 among the textures, after having performed its part ; in the 

 other, it dissolves, disappears, and throws out its contents 

 on a free surface. Now, it will be perceived, that before 

 a cell can perform its functions as a nutritive cell, or as a 

 secreting cell, it must have acted as an absorbing cell. 

 This absorption, too, must necessarily be of a peculiar and 

 specific nature. It is in virtue of it that the nutritive cell 

 selects and absorbs from the liquor sanguinis those parts 

 of the latter necessary for building up the peculiar texture 

 of which the cell is the germ. It is in virtue of this pecu- 

 liar force that the secreting cell not only selects and 

 absorbs, but also in some instances elaborates, from the same 

 common material, the particular secretion of which it is 

 the immediate organ. And it is by the same force that 

 the cell becomes the immediate agent of absorption in certain 

 morbid processes. 



"Absorption,"* says Professor Mtiller, " 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 

 secretion ; the fluids altered by the secreting action being im- 

 pelled towards the free surface only of the secreting mem- 

 branes, and then pressed onwards by the successive portions 

 of fluid secreted. In many organs, for instance in those in- 

 vested 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. 



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



