THE BILE. 329 



theory, essentially the same in both foetal and extra- 

 uterine life ; only, in the former, it is directly excreted, in 

 the latter for the most part indirectly, being, before final 

 ejection, modified in its absorption from the intestines, and 

 mingled with the blood. 



The change from the direct to the indirect mode of 

 excretion of the bile may, with much probability, be con- 

 nected with a purpose in relation to the development of 

 heat. The temperature of the foetus is maintained by that 

 of the parent, and needs no source of heat within the 

 body of the foetus itself; but, in extra-uterine life, there is 

 (as one may say) a waste of material for heat when any 

 excretion is discharged unoxidized ; the carbon and hydro- 

 gen of the bilin, therefore, instead of being ejected in the 

 faeces, are re-absorbed, in order that they may be combined 

 with oxygen, and that, in the combination, heat may be 

 generated. 



From the peculiar manner in which the liver is supplied 

 with much of the blood that flows through it, it is probable, 

 as Dr. Budd suggests, that this organ is excretory, not 

 only for such hydro-carbonaceous matters as may need 

 expulsion from any portion of the blood, but that it serves 

 for the direct purification of the stream which, arriving by 

 the portal vein, has just gathered up various substances 

 in its course through the digestive organs substances 

 which may need to be expelled, almost immediately after 

 their absorption. For it is easily conceivable that many 

 things may be taken up during digestion, which not only 

 are unfit for purposes of nutrition, but which would be 

 positively injurious if allowed to mingle with the general 

 mass of the blood. The liver, therefore, may be supposed 

 placed in the only road by which such matters can pass 

 into the general current, jealously to guard against their 

 further progress, and turn them back again into an 

 excretory channel. The frequency with which metallic 

 poisons are either excreted by the liver or intercepted and 



