400 LECTURE XVI. 



tion alone. On the contrary, we see in every case, 

 where fatty products remain stagnant for a considerable 

 time within a closed cavity in which but little inter- 

 change of matter can go on, that the fat sets free cho- 

 lestearine. All the masses of fat which we meet with 

 in the body contain a certain quantity of cholestearine 

 in combination. As to whether the cholestearine which 

 is set free had already previously existed, or whether a 

 real new formation of it takes place in the parts, not 

 a word can as yet be said, inasmuch as no chemical 

 fact has, it is well known, been made out, which throws 

 any light upon the manner in which the formation of 

 cholestearine is effected, or upon the substances, out of 

 which cholestearine may be formed. This much, how- 

 ever, we must hold fast, that cholestearine is a product 

 set free at a late period from stagnating, and, particularly, 

 from fatty matters. 



I may take this opportunity to mention the reaction 

 of cholestearine with iodine and sulphuric acid, which 

 has recently become important, and is similar to that 

 which we have already (p. 31) considered when speak- 

 ing of the cellulose of plants. When, namely, iodine 

 alone is added to cholestearine, no change is seen any 

 more than in cellulose, under similar circumstances ; 

 but when, on the other hand, sulphuric acid is applied 

 to the iodized mass of cholestearine, its plates become 

 coloured and assume, particularly at first, a brilliant 

 indigo-blue tint, which gradually passes into a yellowish 

 brown, until the cholestearine is converted into a brown- 

 ish drop. Sulphuric acid alone produces a fatty-looking 

 substance which is neither cholestearine, nor any special 

 combination of cholestearine and sulphuric acid, but a 

 product of the decomposition of the former. Sulphuric 

 acid alone also produces very beautiful phenomena of 

 colour with cholestearine. 



