Page:Proceedings of the Royal Society of London Vol 60.djvu/472

440 power, dissolving 1 to 5 per cent, of the fat of beef suet at 39° C. The solution becomes viscid, semi-fluid, or completely solid on cooling, and redissolves on warming again. With the filtered contents of the intestine of the pig and rabbit similar results were not obtained, but the fat became altered, being in part converted into fatty acids, and in part giving rise to a voluminous precipitate.

Finely minced, fresh dog’s pancreas (1 gram) was added to bile (10 c.c.), and then the fat of beef suet (0'25 gram) ; the fat completely dissolved in three hours at 40° C.; on cooling, the solution became turbid, and finally semi-solid. In a control experiment, pancreas alone decomposed fat into fatty acids, but did not dissolve it.

The solubilities stated above are quite sufficient to account for the removal of all the fat of the food from the intestine as dissolved fatty acid, since they exceed the concentrations found in the intestine of other materials, such as sugars and albumoses, which are removed in solution. Other experiments, however, on the reaction of the intestine during fat absorption, lead us to think that all the fat is not removed as dissolved fatty acids, but that these are replaced to a variable extent (in some animals, to a very large extent or completely') by dissolved soaps.

We have determined the reaction of the contents of the dog’s small intestine during fat absorption, from pylorus to caecum, to various indicators, litmus, methyl-orange, and phenolphthale'in, and cannot agree with the statement of some other experimenters, that it is acid throughout.* In sixteen experiments on this animal we only once found the reaction acid to litmus up to the caecum, and this was an obviously poor experiment, in which the intestine was almost empty. The reaction to litmus at the pylorus is neutral, faintly acid, or faintly alkaline; from here onwards the acidity increases, reaches a maximum about the middle of the small intestine, and then becomes less acid, to change to alkaline at a point situate two-thirds to three-fourths of the way along the intestine; from this point on to the caecum the alkalinity increases.!" The reaction to methjlorange and phenolphthale’in explains this; the intestine is alkaline to methyl-orange all the way from pylorus to caecum, and equally com-

Chem.,’ vol. 9, 1885, pp. 572, 574. + There is usually a reversion to an acid reaction in the large intestine, in v luc i case the contents of the ca?cum are almost neutral.
 * Cash, ‘ Arch. f. Anat. a. Physiol.,’ 1881, p. 386 j Munk, ‘Zeitsch. f. Physiol.