/ • / ssa ge of i in: /■: i r to the la c teals. 45 7 
If a rabbit be killed some hours after a meal of oats, a certain amount of fat is 
shown to be in process of absorption by the whiteness of the lacteals, but the 
reaction of the contents of the small intestine is always markedly alkaline. 
It is probable, then, that in all animals a greal part of the fat is 
absorbed dissolved in the form of soaps; but in some animals a part 
is also absorbed as dissolved fatty acids, while in others the entire 
quantity leaves the intestine in the form of soaps. 
These various theories as to the form in which fats enter the epithelial 
cell, may be summarised as follows: — 
Emulsion theories. — 1. A small percentage of the fat is split up into 
fatty acids and glycerin, the fatty acids unite with the alkaline basis of the 
mixed secretions present in the intestine, and the rest of the fat is thereby 
converted into an emulsion, which is absorbed by the columnar cells. 
2. A considerable part of the fat is split up into fatty acids and glycerin, 
and absorbed as emulsified fatty acids and glycerin, which are synthesised 
to neutral fats by the columnar cells. 
Solution theories. — 1. All the fat is split up into fatty acids and glycerin; 
the fatty acids combine with alkaline bases to form soluble soaps; these and 
the dissolved glycerin are absorbed in solution, and synthesised to neutral 
fats in the columnar cells. 
2. All the fat is split up into fatty acids and glycerin; the fatty acids 
are dissolved as such by the intestinal fluid (the bile being that constituent 
which gives this solvent property to the fluid), these dissolved fractions of the 
fat are absorbed by the columnar cells, and by these are synthesised again to 
neutral fats. 
3. The processes indicated under solution theories 2 and 3 probably 
mutually replace each other to a variable extent in some animals, but in 
others absorption takes place entirely in the form of soaps. 
Passage of the fat from the epithelial cells to the lacteals. — 
In whatever form the fat passes into the columnar cells, it is certain 
that it is here converted again into fat. During active fat absorption 
these cells become gorged with fat globules of varying dimensions. It 
is agreed by all observers that this fat passes from the epithelium to 
the lacteals in the form of an emulsion, but there is some difference of 
opinion as to the fashion in which it is conveyed. 
It has already been stated that the tissue of the villi, especially 
during active fat absorption, contains immense numbers of leucocytes. 
These are found not only in the subepithelial tissue, but between the 
epithelial cells. The number in this position is greatly increased during 
absorption, and at this time lymphoid cells occur also in the lacteals, 
but "are found more numerously in the lacteals of the villi than in 
those which are more deeply seated, and, most numerously of all, near 
the blind end of the lacteal. That they pass into this vessel from 
the surrounding lymphoid tissue is certain, for a lymphoid cell may 
often be seen, fixed by the reagent employed for hardening the tissue, 
in the act of passing through the wall of the lacteal." 1 After a meal 
containing fat, these lymphoid corpuscles contain granules, which stain 
black with osmic acid ; many of these are soluble in ether, so that they 
are unquestionably composed of fat. 
1 Schafer, Intermit. Monatschr. f. Anal. u. Histol., Leipzig, 1885, Bd. ii. S. 6. The 
greater part of the description of the carriage of fat by leucocytes, between epithelium and 
lacteal, given in the text, is abstracted from this source. 
