CHAP. V.] THE BILE AS A DIGESTIVE SECRETION. 



351 



matters, which are certainly clctee derivations of the bile colouring 

 matters ; in the second case much bilirubin. 



It has thus been proved, by 'a number of distinct but correlated 

 arguments, that the bilirubin of the bile is a derivative of the blood 

 colouring matter. When discussing the mode of production of 

 jaundice, we shall shew that, if we except the local origin in blood 

 extravasations, bilirubin is only formed in the liver. 



SECT. 2. DISCUSSION OF THE QUESTION WHETHER THE BILE is 

 TO BE CONSIDERED A DIGESTIVE SECRETION. THE ACTION 

 OF THE BILE ON CARBOHYDRATES, PROTEIDS AND FATS. 



Preliminary Observations. 



The bile differs from the saliva, the gastric juice, and the pan- 

 creatic secretion in that, if we except altogether insignificant traces 

 of a diastatic enzyme, it contains no ferment capable of dissolving, or 

 effecting the hydrolytic decomposition of, carbohydrates, proteids, or 

 fats. Nevertheless, although the bile unquestionably subserves 

 excretory functions, it also plays an auxiliary and not unimportant, part 

 in the complex digestive processes of the small intestine. 



Two interesting anatomical considerations may be adduced, of 

 which the first establishes the excretory function of the bile, whilst 

 the second raises a strong presumption in favour of the importance 

 of the bile in the digestive process : 



Firstly. During the third month of foetal life 1 , long before other 

 digestive secretions are found out (at a time therefore when digestive 

 acts are yet entirely in abeyance), the liver whose importance for the 

 economy at this period is, doubtless, represented by its relatively 

 enormous development, commences to secrete bile which accumulates 

 in the intestine and forms a large part of the meconium 2 , which is dis- 

 charged at an after birth. This fact argues strongly in favour of the 

 indispensable excretory functions of the bile. 



Secondly. The bile duct in all animals opens into the commence- 

 ment of the intestine, into the duodenum, either at the same place 

 as, or above the, principal pancreatic duct. 'If,' argues Bunge 3 , 'the 

 bile were an excretion we should expect the ductus choledochus to 

 open into the lower end of the rectum, just as the ureter opens into 

 the cloaca in the lower vertebrates. It is impossible not to believe 

 that bile, in its long passage through the intestines, must have some 

 serious duties to perform.' 



1 Zweifel, ' Untersuchungen iiber den Verdauungsapparat des Neugeborenen,' 

 Berlin, 1874, Centralblatt /. d. med. Wissenschaft, 1874, no. 59; Preyer, Specielle 

 Physiologic des Embryo, Leipzig, 1885. 



2 Zweifel, ' Untersuchungen iiber das Meconium.' Archiv f. Gynakologie, Vol. vn. 

 p. 474. 



3 Bunge, Physiological and Pathological Chemistry, Vol. i. p. 213. 



