90 PHYSIOLOGY. 



the lobules, connecting them together, and sending branches towards 

 the interior of each. Their mode of termination, and their relation to 

 the hepatic cells forming the parenchyma of the gland, are as yet un- 

 explained. These cells of the liver, which are the real agents in the 

 secreting process, are of a flattened spheroidal form, lying in piles, 

 which seem to be directed from the circumference to the centre of each 

 lobule. Their diameter is from 1 -1500th to l-2000th of an inch ; they 

 have a distinct nucleus, and a well-marked biliary tinge, and contain a 

 granular amorphous matter with a few small adipose granules. They 

 are easily obtained in a separate condition by scraping a piece of 

 fresh liver. 



The secretion of bile is probably a constant operation, although it 

 may vary in quantity at different times. It may be discharged at 

 once into the intestine, or it may regurgitate into the gall-bladder, as 

 it probably does when the intestine is empty and there is no stimulus 

 there to provoke the flow. In the gall-bladder the bile undergoes a 

 concentration by the absorption of its watery parts ; it is also mixed 

 with the mucus secreted from its walls. 



The chemical composition of the bile is unsettled. It is of a yel- 

 lowish green colour, viscid, and slightly bitter. It combines readily 

 with water, mixes freely with oil or fat; and foams, when stirred, 

 like soapy water. The proportion of solid matter is usually from 9 

 to 12 per cent; nearly the whole of this consists of substances pe- 

 culiar to the bile. 



Three distinct substances are found in the biliary matter: — Cho- 

 lesterine, or bile fat, resembling spermaceti, and consisting princi- 

 pally of carbon and hydrogen. Bilic acid^ a compound of soda 

 with a peculiar organic body, now regarded in the light of a fatty 

 acid, and described by some chemists as choleic acid, bilin, picromel, 

 &c., and a colouring matter called hiliverclin, a substance identical 

 with the chlorophyl of plants. In addition to these the bile contains 

 some earthy salts. 



Uses of the hiU. — A portion unquestionably passes off* with the 

 faeces; this, which includes the colouring matter, is that which would 

 be injurious if retained in the blood, and is probably excrementitious. 

 The soajjy portion seems to act by rendering the fatty matters solu- 

 ble, and thus enabling them to be absorbed by the lacteals. The 

 importance of the bile, (probably the soapy portion of it,) has been 

 shown by Schwann, who prevented it from passing into the in- 

 testine, and found that the animals wasted, and at last died in a 

 state of emaciation. The bile may also perform another function, 

 as before stated, — the transformation of sugar into fatty matter. It 

 is not improbable that this change may take place injhe liver ; since 

 in animals fed upon grape sugar, this substance has been found in 

 the portal vein but not in the hepatic. The 'fatty matter of the bile, 

 when reabsorbed with that of the newly" ingested food, is probably 



