THE BILE. 



325 



its physiology is, perhaps, better illustrated by its ultimate 

 elementary composition. According to Liebig's analysis, 

 the biliary matter, consisting of bilin and the products of 

 its spontaneous decomposition yields, on analysis, 76 atoms 

 of carbon, 66 of hydrogen, 22 of oxygen, 2 of nitrogen, 

 and a certain quantity of sulphur.* Comparing this with 

 the ultimate composition of the organic parts of blood, 

 which may be stated at C 48 H 36 N 6 O 14 with sulphur and 

 phosphorus it is evident that bile contains a large pre- 

 ponderance of carbon and hydrogen, and a deficiency of 

 nitrogen. The import of this will presently appear. 



TESTS FOU BILE. A common test for the presence of 

 bile consists of the addition of a small quantity of nitric 

 acid, when, if bile be present, a play of colours is produced, 

 beginning with green and passing through various tints 

 to red. This test will detect only the colouring matter of 

 the bile. 



The best test for the bilin is Pettenkofer's. To the liquid/; 

 suspected to contain bile must be added, first, a drop or two 

 of a strong solution of cane-sugar (one part of sugar to 

 four parts of water), and immediately afterwards sulphuric 

 acid, to the extent of about two-thirds of the liquid. On 

 first adding the acid, a whitish precipitate falls ; but this 

 redissolves with a slight excess of the acid, and on the 

 further addition of the latter there appears a bright cherry- , 

 red colour, gradually changing through a lake tint, to a dark j 

 purple. 



The process of secreting bile is probably continually going 

 on, but appears to be retarded during fasting, and accele- 

 rated on taking food. This was shown by Blondlot, who, 



* The sulphur is combined with the taurin one of the substances 

 yielded by the decomposition of bilin. According to Dr. Kemp, the 

 sulphur in the bile of the ox, dried and freed from mucus, colouring 

 matter, and salts, constitutes about 3 per cent. 



