258 DIGESTIVE SYSTEM. 



change takes place, which seems to be the signal of the death 

 of the cell. It therefore appears probable, that the columnar 

 epithelium, which we are considering, is near its end, that it 

 will soon fall into decay, and that an actual moulting of the 

 epithelium of the mucous will take place : this is what, we 

 find, actually occurs. When the chyme contains fatty mat- 

 ters, this effect is still more apparent; the white is more 

 brilliant and the fat globules larger : but here, too, the whole 

 surface disappears, and a new epithelium takes its place. 1 



This whitish appearance and turgescence begin at the free 

 base of the epithelium, extending gradually to'its depth, and 

 spreading over the whole villus (Fig. 69, C). It is always, 

 however, the epithelium of the summit of this papilla which 

 first becomes whitish and swollen, thus imparting to the vil- 

 lous projection a peculiar appearance, which enables us to 

 understand what Lieberkiihn saw, and explained by giving 

 it the name of ampulla (small aspiratory reservoir of the 

 chyle). The change in the mandrel of the villus follows 

 that in the epithelium ; and as the latter becomes granular, 

 and is about to fall, the summit of the villus appears to change 

 into a cluster of small drops of fat, which are seen first in the 

 body, and then at the base of the villus, and are often more 

 or less regularly ranged in rows. This would lead to the 

 supposition that there are separate vessels, but it seems more 

 probable that phenomena of nutrition are taking place in the 

 plasmatic elements of the mucous, and that they are accom- 

 panied by metamorphoses similar to those which we have 

 seen in the epithelium. These phenomena are still more 

 striking when the intestinal fluid contains a large quantity 

 of fat (Fig. 69, C, D). 



This appearance is sometimes modified, especially in the 

 dog (Fig. 69, B), by the deformation of the villus ; but this is 

 only an accessory phenomenon, and is caused by the con- 

 traction of the smooth muscular fibres. The body of the 

 villus, in fact, contains rudimentary cantractile elements, 

 arranged, especially around the central chyliferous vessel, 

 in striae longitudinal to the axis of the villus ; they are 



1 See Kiiss, " Gazette Medicale de Strasbourg." 1846, p. 38, 

 Sur F absorption. 



Finck, " Sur la Physiologic de 1'Epithelium Intestinal." These 

 de Strasbourg, 185 1, No. 324. 



L. Lereboullet, " De 1'Epithelium Intestinal au point de vue de 

 1' Absorption des Matieres Grasses." These de Strasbourg, 1866, 

 No. 957. 



