782 FORMATION OF BILIRUBIN. [BOOK H. 



stated above, no accumulation of bile in the blood after extirpation 

 of the liver, but that operation prevents the appearance of bile 

 pigment in the urine as a consequence of the presence of free 

 haemoglobin in the blood ; the urine in such a case contains merely 

 haemoglobin. And it is maintained that, whenever bile-pigment 

 appears in the urine as the result of haemoglobin being dissolved 

 in the blood plasma, the small bile-passages are found so choked 

 with bile and the flow of bile away from the liver thereby so 

 obstructed as to justify the view that resorption of bile has taken 

 place from them into the lymphatics and so into the blood. 



478. We have however no positive evidence that, under 

 normal circumstances, haemoglobin is brought to the liver in a 

 free condition, that is to say, dissociated from the red corpuscles 

 and dissolved in the plasma. Even if we admit as probable the 

 view that red blood corpuscles come to an end somewhere in the 

 blood stream, we must confess that the plasma of the general blood 

 stream does not contain any quantity of haemoglobin sufficient to 

 be detected by the spectroscope, the faint yelloAv colour of serum, 

 and presumably of plasma, being due to a special pigment. Having 

 regard to the disintegration of red corpuscles which takes place in 

 the spleen, it might be imagined that haemoglobin set free in that 

 organ would be carried to the liver in the plasma of the blood 

 of the splenic vein; but even that plasma does not contain any 

 such amount of haemoglobin as can be detected ; we may add that 

 the changes of the red corpuscles in the spleen appear to go far 

 beyond the mere liberation of haemoglobin and are rather of the 

 nature of disintegration. Nor have we evidence of haemoglobin 

 existing in free condition in the blood leaving any other organ. 

 If we may trust to this negative evidence, we should be led to 

 suppose that the liver itself has the power of extracting the 

 haemoglobin from the red corpuscles (and this so far as we 

 know means destruction of the corpuscles) as these traverse its 

 capillaries preparatory to the conversion of that haemoglobin into 

 bilirubin. But we have no satisfactory direct indications of the 

 occurrence of such a remarkable process ; and we may hesitate to 

 accept the negative evidence touching the presence of haemoglobin 

 in blood plasma as conclusive. A quantity of haemoglobin, quite 

 beyond detection in each c.c., or even 100 c.c., of plasma brought 

 to the liver, might, seeing how great is the blood flow through the 

 liver, reach in the 24 hours an amount adequate to furnish all the 

 bilirubin secreted during that period. And it must be remembered 

 that the whole change from red corpuscle to bilirubin may occasion- 

 ally take place quite apart from the liver, as shewn by the presence 

 of haematoidin in old blood-clots. 



479. The formation of the bile-acids. About this again we 

 know very little. Taking glycocholic and taurocholic acids as the 

 typical bile acids, recognizing ( 246) that these arise from the 

 union of cholalic acid with glycin and taurin respectively, and re- 



