270 EXCRETION. 



mens, the crystals are generally few in number and isolated. 

 The plates of cholesterine are frequently marked by a cleav- 

 age at one corner, the lines running parallel to the borders ; 

 and frequently they are broken, and the line of fracture is 

 generally undulating. Lehmann attaches a great deal of 

 importance to measurements of the angles of the rhomboid. 

 According to this author, the obtuse angles are 100 30', and 

 the acute 79 30V "We have examined a great number of 

 specimens of cholesterine, extracted from the blood, bile, 

 brain, liver, and occurring in tumors, and have not observed 

 that the crystals have definite angles. Frequently the 

 plates are rectangular, and sometimes almost lozenge-shaped. 

 It is by the transparency of the plates, the parallelism of 

 their borders, and their tendency to break in parallel lines, 

 that we recognize cholesterine. Lehmann seems to consider 

 the tablets of this substance as regular crystals having in- 

 variable angles. From examination during crystallization, 

 it seems more probable that they are not crystals, but frag- 

 ments of micaceous sheets, which, from their extreme tenuity, 

 are easily broken. In examining a specimen from the me- 

 conium, which was simply extracted with hot alcohol, it was 

 easy to observe a transparent film forming on the surface of 

 the alcohol soon after it cooled, and this, on microscopic 

 examination, in situ, disturbing the fluid as little as possible, 

 was found to be marked by long parallel lines. When the 

 fluid had partially evaporated, the crust became broken and 

 the fragments took the form of the ordinary crystals of cho- 

 lesterine, but they were larger and more regular. The tab- 

 lets were exceedingly thin, and regularly divided into deli- 

 cate plates, with the characteristic corner-cleavages of the 

 cholesterine ; and as the focus of the instrument was changed, 

 new layers were brought into view. 



Crystals of cholesterine melt at 293 Fahr., but are formed 

 again when the temperature falls below that point. Accord- 

 ing to Lehmann, they may be distilled in vacuo at 680, 



1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 244. 



