30 MANUAL OF HISTOLOGY. 



decomposition. Besides, however, they may occur pathologically in the 

 living body, e.g., in the organs just mentioned, the brain and spinal cord, 

 whose sustentacular connective tissue may contain them in abundance. 

 They are met with also in the prostate of considerable size. 

 KEMABKS. Sfrw&er in the Zeitschr, fur Chemie, 1868, S. 437. 



21. 

 Cholestearin, C 26 H .4 + H 2 . 



Sensible of the difficulty of appropriately grouping animal substances, 

 for the present we insert here monatomic alcohol, with the distinct charac- 

 ters of a decomposition product. 



This compound (fig. 6) has a very characteristic crystalline form ; it is 

 found, namely, in extremely thin, rhombic tables, whose obtuse angle is 

 100 30', and acute, 79 30', according to C. Schmidt. These are 

 usually arranged overlapping each other, and are frequently broken at 

 the corners. 



Cholestearin is completely insoluble in water, but perfectly soluble in 



boiling alcohol, ether, and chloroform. It is 

 dissolved in fats and ethereal oils ; in the 

 two combinations with soda of the biliary 

 acids and in soap-water important proper- 

 ties in regard to the occurrence in the 

 human body of this otherwise insoluble 

 substance. 



Treated with sulphuric acid, crystals of 

 cholestearin become of a rusty or purple 

 colour, beginning at the edges. In concen- 

 trated acid, on the other hand, they dis- 



Fig. 6.-Crystai77"choiestearin. solve gradually, forming coloured globules. 

 The addition of iodine to these reagents 

 produces more lively colours still. 



Cholestearin, which has been recently met with widely distributed 

 throughout the vegetable kingdom (Beneke, Kol~be), has no histogenic pro- 

 perties, its crystallizability seeming to render it but little fitted to enter 

 into the structure of tissues. It possesses entirely the nature of a mutation 

 product whether of the fats or of azotised histogenic substances is still 

 undecided. It is extensively distributed throughout the system, but is 

 only excreted in minute quantities, so that some further decomposition 

 still quite unknown to us may be inferred. 



It is found in the blood, but in small amount, and in most of the 

 animal fluids, especially in bile, but not in the urine. It is also met 

 with in the substance of the brain, as a constituent of myelin, in patholo- 

 gical fluids and tumors, and in biliary calculi. Passing off with the 

 bile, it is found in the excrements. 



E. The Carbhydrates. 



22. 



These substances bear this not very happily chosen name on account 

 of their containing oxygen and hydrogen in the same proportions as in 



