THE BILE. 241 



etted hydrogen through it. These two acids are found in 

 the bile combined with soda. 



Glykocholate of soda has the formula Na 0, C 52 H 42 N0 n . 

 If giykocholic acid be boiled with a dilute solution of 

 potash, it is decomposed into cholic acid and glycine, hence 

 its name. 



Taurocholic acid contains sulphur, and has the composition 

 C 62 H 45 NS 2 O u ; its soda salt is not crystallizable. 



The biliary acids of the dog differ from those of the ox, in 

 that neither of them is precipitated by acetate of lead, whereas 

 both are precipitated by sub-acetate of lead. 



The pig's bile contains no crystallizable substance, the 

 ether precipitate being entirely resinous in appearance. 



The colouring matter of the bile, called biliverdine, has 

 been little studied, and we do not even know approximative^ 

 its proportion in the bile. The bile of most of the carnivora 

 has a yellow colour; that of the herbivora a green. There 

 appear to be two varieties of colouring matter, viz., a brown 

 and a green ; the former seems to be converted into the latter, 

 if the bile remains in the gall-bladder. 



Cholesterine is a constant constituent of the bile, and it 

 appears to be kept in solution by the taurocholates. 



The mineral ingredients of bile are chloride of sodium, 

 phosphate of soda, carbonate of soda, phosphate of lime, and 

 magnesia. 



Tests for Bile are two in number. The one consists in 

 the action of nitric acid, which causes it to assume a variety 

 of colours, viz., green, violet, red, and yellow; it is unsatis- 

 factory, however, as it only proves the existence of bile 

 colouring matter, which it causes to assume these varieties 

 of colour. The other test, generally known by the name of 

 Pettenkofer's test, is much more satisfactory, as it demon- 

 strates the existence of one or both bile-acids. It consists in 



R 



