514 LECTURE XXII. 



ents which are found in other parts of the body as well. These are chole- 

 sterol, lecithin, soaps, neutral fats, and urea. Conjugated glucuronic acids 

 have also been detected in the bile. The salts of the bile-acids are of 

 chief interest to us. We shall come back to the bile-pigments when we 

 come to consider the pigments of the blood from which the former result. 

 That the bile-acids owe their formation unquestionably to the activity of 

 the liver, is evident from quite a number of observations. If, for exam- 

 ple, the liver be entirely extirpated from a frog, no more bile-acids can be 

 detected subsequently in its tissues. If they were produced by other 

 organs, the acids would be formed after the removal of the liver, unless 

 it is to be assumed that the liver acts in conjunction with other organs in 

 their production, and that it produces either the original stages or at 

 least some essential stage in their formation. Although we are compelled 

 to assume the existence of such reciprocal relations in a great many 

 cases, still at present it may be regarded as proven that the liver is the 

 sole place in which these bile-acids are formed. Any other assumption 

 would appear less probable. In dogs also, it may be shown that the 

 preparation of the bile is a function of the liver-cells. If the bile duct 

 is ligated, there is first of all an accumulation of bile. Certain con- 

 stituents of the latter then pass into the lymph, and are carried by means 

 of the thoracic duct to the blood. Now if the thoracic duct be ligated as 

 well as the bile duct, no more bile-acid can be detected in the blood. 



The bile-acids belong to two groups; namely, the glycocholic and tauro- 

 cholic groups. The members of the first group contain carbon, hydrogen, 

 and nitrogen, and by their hydrolysis yield glycocoll and a non-nitroge- 

 nous acid; while those of the other group contain sulphur in addition to 

 the above elements, and on hydrolysis they yield taurine, and similarly a 

 non-nitrogenous acid. The constitution of the nitrogen-free acid which is 

 contained in both groups of bile-acids, and which, moreover, appears to 

 have a different composition in different bile-acids, has not yet been 

 fully explained. In general, such an acid is known as cholic or cholalic 

 acid. We will merely mention the fact that the acid has been assumed 

 repeatedly to be related to cholesterol, but this relation has never been 

 established satisfactorily. 



The relative amounts of these two groups of acids vary according to 

 the species of animal, and in fact one or the other group may be missing. 

 Glycocholic acid, C26H 43 NO6, is always present in human- and ox-bile. 

 Besides this a second acid, glycocholeic acid, 1 is frequently found which 

 differs from the first with regard to the " cholalic acid " which it yields; 

 in this case the acid is known as choleic acid. The solubility relations of 



1 V. Wahlgren: Z. physiol. Chem. 36, 556 (1902). 0. Hammarsteii: ibid. 43, 109 

 (1904). H. P. T. Oerum: Skandin. Arch. Physiol. 16, 273 (1904). C. Gundelach and A. 

 Strecker: Ann. 62, 205 (1847). 



