On the other hand, there are good reasons for regarding the reception of fatty matters as a much more complex phenomenon, and the result of what we may venture to call more vital processes. For the way in which ether and other solvents act upon the chyle appears to prove, that the fatty contents of its molecules are still oily ; and not saponified, like such diffused fluids. And while the position of the capillary plexus,and the rapid ity and quantity of its stream, render it pro bable that any merely diffusive action would disproportionately affect the blood—which by the way is often more alkaline than the chyle —a chemical and physical comparison of these two fluids would seem to show that the re verse is actually the case : that a larger quan tity of fat is taken up by the lacteals than by the blood-vessels. This view is also con firmed by the results of violent inflamma tion 40, or of great interference with the blood vessels : — changes, neither of which would probably have much direct effect on the physical action of an independent system of tubes, but which are nevertheless alleged entirely to pre vent the formation of chyle. In any case, it would seem that there are strict limits to the quantity of fatty matter which can be absorbed. Hence when the amount of fat present in any particular region at all exceeds what its villi can take up, it is passed on to other portions of intestine ; fltiling absorption by which, it is ultimately discharged unchanged in the flexes.
Intestinal Follicics.t —We pass on to the description of a class of structures which are essentially closed sacs; and which, represented in the stomach by the lenticular glands, pervade all the remainder of the intestinal canal under the two forms of solitary and agminate fol licles: the latter being, as their name implies, essentially clusters of the former.
Agntinate follicles.— Of the very' numer ous§ names which have been bestowed upon these follicles, that above made use of seems preferable ; since it best connotes both their structure and arrangement. There are generally about twenty clusters of these agminate follicles scattered throughout the small intestine. Their shape is commonly that of an oval, having a length about twice its width. They are situated on the free border of the bowel, or opposite to the attachment of its mesentery ; and usually correspond to about the lower three-fifths of the small intestine, or to that part of it which is regarded as the ileum. Hence they have been looked upon as, in a certain sense, characteristic of this region. But they some times extend into the jejunum, being scattered sparingly throughout its lowest segtnents. And they may rarely be found even in the duodenum. In such cases, their entire number is usually about twice or thrice that of the average given above.
But amid all their variations of number, size, and extent, the agminate follicles seem to retain a certain predominant relation to the end of the ileum. For it is here that they are both largest and most numerous. And while in the remainder of the small intestine, their length is usually rather under than over an inch, nothing is more common than to find the immediate neighbourhood of the ilio-csecal valve occupied by a single irregular cluster ;— which has a length of two, three, or even four inches, and a width which carries it round i-tis or iths of the inner circumference of the intestinal tube.
bowel by reflected light, at a place corre sponding to a cluster of agminate follicles, vve see that its surface (which is raised above the rest of the intestine, but has no very sharp line of demarcation from it) is occu pied by a number of irregular shallow de pressions (b,fig. 267.), at tolerably uniform dis tances from each other. But when inspected by transmitted light, these fossm are replaced very characteristic appearance.* In like manner, the villi in their immediate bourhood often appear to radiate outwards by comparatively opaque grains (b,'b,fig. 269.), of about the size of a millet seed ; the ar‘ore gation of which renders the whole cluster very distinctly visible by this mode of exami nation. Finally, the cluster may often be recognised externally, from the bulg,ing of the pentoneal coat which it causes in this situa tion. Indeed, its constituent follicles may sometimes be seen glimmering through the delicate muscular tunic.
Each such cluster is composed of a number of follicles, varying from twenty or thirty in the smaller, to at least one or two hundred in the larger, specimens. A careful examination of the mucous surface shows that the depressions just mentioned do not lead to any apertures, but are terminated by a smooth surface, the convexity of which somewhat diminishes their own depth. It is only at the margins, and in the intervals, of these fossm, that we find the tubes and villi proper to the small in testine. And both of these latter structures are somewhat modified. Those tubes which immediately surround each depression have a circular or elliptical arrangement ; so that their orifices generally form a ring of ten to twenty tubes in the fossa (around a, fig. 269.), and thus give rise to a from a point corresponding to the centre of the fossa. And both they, and those more equidistant to the several follicles, are very different from the villi seen elsewhere :— being fewer (b, fig. 269; a, fig. 270.), shorter, of more irregular form, and often confluent at their bases.