110 DIGESTION. LECT. V. 



then, is a fresh proof that, in the intestines, the solvent ac- 

 tion on the neutral azotised substances ceases. 



Absorption of Fat. It is difficult to determine precisely 

 by analogies derived from chemistry, what becomes of the 

 fatty substances after they have passed out of the stomach. 

 It is certain that they are there absorbed, and that the chy- 

 liferous vessels may be considered as almost exclusively 

 charged with this function. 



Here are some experiments by means of which I have 

 endeavoured to diminish the obscurity which hangs over 

 this part of the digestive process. I put into a matrass a 

 solution of 300 grammes [= 9 oz. 132 grs. troy] of dis- 

 tilled water, l T 3 <r grammes [about 20 grains troy] of caustic 

 potash. This solution has not any perceptible alkaline 

 taste, and acts very feebly on litmus paper ; it is a liquid 

 whose alkalinity is about equal to that of the lymph and 

 chyle. By means of a salt water bath, I expose the ma- 

 trass to a temperature of from 35 to 40 centig. [= 95 

 to 104 Fahr.;] I then add some drops of olive oil and 

 shake the mixture ; it instantly becomes so milky that it 

 might be mistaken for milk itself. The liquid thus ob- 

 tained, when left to itself, preserves its analogy to milk, 

 and separates into two layers, the one more opaque at the 

 top, in which are evidently small globules of fatty matter ; 

 the other, below, and less opaque, although still having a 

 milky aspect. I have filled a piece of intestine with this 

 species of emulsion, and plunged it into the alkaline solu- 

 tion already described, whose temperature was maintained 

 at from -f 35 to 40 centigs. [= 95 to 104 Fahr.] 

 After some time, the latter becomes turbid and acquires the 

 characters of the interior emulsion. We, therefore, pre- 

 sume, that a portion of the emulsion has passed through the 

 membrane and become diffused externally. 



I may mention to you another experiment which appears 



