368 LECTURE XV. 



the interior of the villi we generally find the network 

 of blood-vessels a little below the surface (Fig. 109, 

 A, v, v), whilst in its axis there is a tolerably wide cana- 

 licular cavity with a blunt extremity, the commence- 

 ment of the lacteal vessel, as far as it can at present be 

 determined with certainty (Fig. 109, A, c). At the 

 periphery of the villi Briicke has discovered a layer of 

 muscular fibres, which is of great importance in diges- 

 tion, inasmuch as by its help an approximation of the 

 apex of the villus to its base, a shortening is effected, 

 as may very readily be seen. Upon cutting off villi 

 from the intestine of an animal just killed, they 

 may be seen under the microscope to contract, become 

 wrinkled, thicker and shorter (Fig. 109, B) ; thereby a 

 pressure from without inwards is manifestly produced, 

 which promotes the onward movement of the juices. 

 So far the matter is tolerably clear, only what sort of 

 a structure the rest of the parenchyma has, it is ex- 

 tremely difficult to see. Upon the outer side of the 

 muscular layer, smallish nuclei are seen, which, as I 

 pointed out many years ago, are now and then pretty 

 distinctly enclosed in fine, cellular elements. But 

 whether these parenchymatous cells anastomose with 

 one another so as to form a special network, I am 

 unable to say. During the process of absorption it- 

 looks as if the fat which keeps penetrating farther and 

 farther into the interior of the villi, filled up the whole 

 parenchyma.* At last it reaches the central lacteal, and 

 there the regular current of chyle begins. 



The whole process therefore presupposes an emulsive 

 condition of the fat, which penetrates through the parts 



* I have quite recently convinced myself by the examination of transverse sec- 

 tions of villi, filled with chyle, in man, that the fat does not lie scattered in the 

 parenchyma, but forms deposits in the interior of special minute cavities (cells?). 

 Note to the Second Edition. 



