OF THE INTESTINAL VILLI. 7 



traced at the free extremity of the villus, as it passed from the 

 surface of one vesicle on to that of another.* The vesicles push- 

 ing the membrane forward, and grouped together in masses on 

 its attached surface, gave the extremity of the villus the appear- 

 ance of a mulberry 7 . When viewed on a dark ground as an 

 opaque object, the point directed to the light, a villus in this con- 

 dition is remarkably beautiful, the play of the light on the surface 

 of the highly refractive semi-opaque and opalescent vesicles, 

 giving them the appearance of a group of pearls. 



In villi turgid with chyle, which have been kept for some time 

 in spirits, the contents of the vesicles are opaque, the albumen 

 having become coagulated. 



To understand the part which the vesicles of the villus play in 

 digestion, it is necessary to be aware of certain of the functions 

 of the cell, with which physiologists are yet unacquainted. Not 

 only are these bodies the germs of all the tissues, as determined 

 by the labours of Schleiden and Schwann, but are also the imme- 

 diate agents of secretion. A 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 func- 

 tion ; 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 sur- 

 face. Now, it will be perceived, that before a cell can perform 

 its function as a nutritive cell, or as a secreting cell, it must have 

 acted as an absorbing cell. This absorption, too, must neces- 

 sarily be of a peculiar and specific nature. It is in virtue of it 

 that the nutritive cell selects and absorbs from the liquor san- 

 guinis 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 peculiar 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 



* Mr. Bowman in the Article " Mucous Membrane" Cyclopedia of Anatomy, does not admit 

 this portion of the membrane. It certainly cannot be detached as a separate membrane. 



