BILE ACIDS AND PIGMENTS. 563 
Kunkd, 1 from similar experiments on dogs, concluded that a definite 
pari of the sulphur taken in the diet is excreted in the bile, but the 
increase in biliary sulphur occurs two or three days after the ingestion, 
and Qot upon the s.nnr day, as is the case with the sulphur of the urine. 
( )i the sulphur of the food, from 8 to 30 per cent, is excreted in taurine. 
In man on an ordinary diet, aboul 33 grms. of urea with 15 grms. of 
nitrogen are daily formed, while only about 10 grms. of bile acids with 
about 0*3 grms. of nitrogen are excreted. The increased ingestion of 
proteids leads to a proportionate increased excretion of urea, and any 
increase in the bile acids is necessarily so small that it may readily 
be overlooked. Similarly, any increased decomposition of the proteids 
of the tissues leads to a proportionately increased excretion of the 
nitrogen in the form of urea, and any increase in the bile acids which 
may occur must be very trifling. 
Whether the bile acids which are absorbed from the intestine can 
be again excreted by the liver cells, has been investigated by injecting 
into the blood of animals a bile salt differing from that which is normally 
present. In dogs the taurocholate of soda is the normal salt of the 
bile. After injecting glycocholate of soda, Prevost and Binet,' 2 and 
Weiss 3 found it in the dug's bile. Socoloff, 4 on the other hand, failed 
to detect it after it had been injected. Huppert 5 observed that the 
injection of glycocholic acid increases the amount of bile acids in the 
bile. The experiments of Eosenberg 6 show that the administration of 
bile salts causes an increased secretion of bile with a marked increase 
in the solids. They appear to be the only substances which produce 
this result, and since the bile salts are the most abundant solids of bile, 
it seems fairly certain that they are absorbed, and re-excreted from the 
blood by the liver. 
Bile pigments.— The pigments must be produced in the liver cells, 
since the secretion from the bile passages is entirely destitute of colour- 
ing matter. 7 They are formed from the haematin moiety of the haemo- 
globin molecule. The injection of free haemoglobin into the blood, 8 or 
the setting free of haemoglobin by solution of the red corpuscles, 9 rapidly 
leads to a great increase of the bilirubin of the bile. Minkowski and 
Naunyn, by experiments upon birds, 10 have confirmed these observations. 
They further found that if the liver is excluded from the circulation 
the formation of bilirubin does not take place. They thus showed that 
bilirubin is actually produced in the liver cells. The iron-containing 
part of the haematin molecule appears to be split off and retained in 
these cells, giving rise to the accumulation of iron in the liver, which 
follows the disintegration of red corpuscles. 11 
Not only do the liver cells manufacture bilirubin, but when this or 
any other bile pigment is present in the blood they take it up and eliminate 
1 Arch. f. d. ges. Physiol., Bonn, Bd. xiv. S. 344. 
2 Compt. rend. Acad. d. sc. Paris, 1888, tome cvi. p. 1690. 
3 Bull. Soc. imp. d. nat. de Moscow, 1884. 
4 Arch.f. d. ges. Physiol., Bonn, 1875, Bd. xi. S. 166. 
5 Arch. d. Eeilk., Leipzig, 1869, Bd. v. 
6 Arch. f. d. ges. Physiol., Bonn, 1890, Bd. xlvi. S. 334. 
7 Birch and Spong, Journ. Physiol., Cambridge and London, vol. viii. p. 37S ; Mayo 
Robson, Proc. Soy. Soc. London, 1890, vol. xlvii. p. 499. 
8 Stadelmann, Arch.f. exper. Path. u. Pharmakol., Leipzig, 1890, Bd. xvii. S. 93. 
9 Afanassiew, Ztsehr. f. klin. Med., Berlin, Bd. vi. Heft 4. 
10 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1886, Bd. xxi. S. 1. 
11 Hunter, Lancet, London, 1892, p. 1262. 
