CHAP. XXV.] THE BILE. 255 



in ether, which dissolves it ; from this solution it crystallizes in 

 plates. It exhibits, when pure, the white crystalline lamellated 

 structure of spermaceti, from which it differs, however, in requiring 

 a much higher temperature for its fusion, namely, 278, and in not 

 forming a soap with potash. Its formula is C 37 H 32 O. Cholesterine 

 is the principal constituent of the gall-stones most commonly met 

 with in the biliary passages. 



The colouring-matter of bile (cholephyrrhin, Berzelius) is one of 

 its most interesting constituents. It varies in different animals, 

 and perhaps in the same animal at different times according to 

 the state of health. Like bilin it decomposes very readily, and 

 therefore cannot be obtained pure ; but it has been procured for 

 analysis from the gall-bladder, where it is sometimes deposited as a 

 yellow substance mixed with mucus. It is very sparingly soluble 

 in most fluids ; scarcely at all in water, and very little in alcohol. 

 Its best solvent is a solution of soda or potass. Such a solution, 

 containing the colouring matter of bile, becomes green on exposure 

 to the air, and on the addition of an acid precipitates green flocculi, 

 which possess all the properties of chlorophyll, the green colouring- 

 matter of plants. To this precipitate, Berzelius has given the name 

 biliverdine. The most remarkable property of the colouring-matter 

 of bile is the play of colours which it is capable of producing under 

 the influence of a mineral acid, especially nitric acid. A little of 

 this acid, added to bile, or to a fluid in which its colouring-matter 

 is dissolved, as it often is, in urine, will change the colour into blue, 

 green, violet, red, and ultimately brown, in a few seconds. It is 

 highly probable, as some chemists affirm, that there exists a great 

 analogy between the colouring-matter of the bile and that of the 

 blood : as there is also, most likely, between these colouring prin- 

 ciples and those of nervous substance, skin, and hair. 



In addition to these constituents, bile contains mucus in con- 

 siderable quantity, to which probably is due its peculiar viscidity 

 It is derived chiefly from the numerous mucous follicles in the 

 bile-ducts, and from the mucous membrane of the gall-bladder, and 

 perhaps also from the debris of the hepatic cells after they have burst 

 and yielded up their contents. According to Berzelius the mucus 

 may be separated by filtering the bile, when a considerable portion 

 of it remains on the filter, and if the bile which has passed through 

 be subsequently subjected to the action of alcohol, the remaining 

 mucus will separate ; or it may be precipitated by the addition of 

 acetic acid. It is to the presence of this mucus in bile that Berze- 

 lius attributes the metamorphic tendency of bilin ; and he affirms 



