INFLUENCE OF LIVER ON PROTEID METABOLISM. 901 



stored within them for a time, passed on into the hepatic blood to reach 

 the general circulation. There is, however, no clear evidence that such 

 storage takes place in the liver, or that if it does the stored proteid 

 undergoes any change within the liver cells. 



When we examine the secretion of the liver, we find that it contains 

 a considerable amount of nitrogenous organic material (bile salts), in- 

 cluding a certain amount of sulphur in organic combination (taurine). 

 These nitrogenous and sulphur-containing materials can only be derived 

 from proteids, and since they are formed in greater amount during absorp- 

 tion of digested products than at other times, it might well be supposed 

 that they may be formed, at least in part, from the absorbed products 

 of proteid digestion. As against this conjecture, we cannot, however, 

 fail to notice that the appearance of these nitrogenous and sulphur- 

 containing materials in the bile salts is accompanied by a considerable 

 amount of material in the form of bile pigments, which can only be 

 derived from the haemoglobin of the red blood corpuscles; and since 

 haemoglobin readily decomposes into haeniatin, which is probably the 

 part directly converted, with elimination of iron, into bile pigment, and 

 a proteid or proteids, it has been conjectured, and with some pro- 

 bability, that the bile acids are actually derived from this proteid part 

 of the broken-down haemoglobin molecule. The only direct evidence 

 that we have of the breaking-down of blood corpuscles within the liver 

 is derived from certain enumeration experiments, which appear to show 

 that the number of blood corpuscles per cubic millimetre passing to the 

 liver is greater than the number per cubic millimetre in the blood flow- 

 ing from the liver. 1 This by itself is not very strong evidence, but it 

 becomes stronger when we remember that the blood flowing from the 

 liver may be expected to contain less water than that which reaches 

 the liver, since there has passed away from it the water of the bile 

 and also a large amount of lymph. Moreover, the constant presence of 

 lecithin and cholesterin in the bile may well be associated with the 

 destruction of red blood corpuscles, which contain, relatively, consider- 

 able amounts of these substances. 



While, therefore, the presence of the bile acids is a clear indication 

 of the breaking-down of proteid in the liver, their presence does not 

 necessarily indicate that such proteid is derived from the blood plasma, 

 bub it is, on the whole, more probable that it arises from the haemo- 

 globin of blood corpuscles. 2 



The storage of glycogen in the liver, under circumstances when it 

 can only be supposed to be formed from proteid, indicates another 

 change which proteids may undergo in this organ. Such a formation 

 of glycogen from proteid probably occurs hardly at all during absorption 

 of a mixed meal, because the amount of carbohydrate absorbed from 

 such a meal would be more than sufficient to account for the glycogen 

 stored in the liver ; but, in the absence of carbohydrate from the food, 

 the proteids may become so split up that one portion of the proteid 

 becomes converted into urea, or into materials which ultimately form 

 urea, and the other portion, possibly by becoming first somewhat 

 broken down and then again synthetised, into glycogen. 



A similar conjecture may be made with regard to the fat which is 



1 Nicolaides, Arch, de physiol. norm, ctpatli., Paris, 1882, p. 531. 



2 According to Kunkel, taurine may be formed from proteids in the tissues generally, 

 and carried to the liver, Ber. d. k. sachs. Geselisch. d. Wissensch., 1875. 



