CHAP. IV,] METHODS OF OBTAINING BILE. 267 



from them. Such a study we propose to make in the case of the 

 liver in Book ill. It cannot be. .undertaken until we have completed 

 our examination of all the processes which have their seat in the 

 alimentary canal. For the latter purpose we are, however, compelled 

 to undertake, at the present stage, a detailed study of the bile. 



SECT. 1. METHODS OF OBTAINING BILE. 



In the case of the bile we do not, in the majority of animals, 

 encounter the difficulties which present themselves in the case of 

 the other secretions of the alimentary canal, when we desire to ob- 

 tain them in a state of purity. In vertebrate animals generally, there 

 exists in connection with the hepatic duct ' a unilateral csecal diver- 

 ticulum ' the gall-bladder, in which, during the periods when a con- 

 tinuous flow of bile into the intestines is not required, the secretion 

 may accumulate, and whence we usually obtain it for the purposes 

 of chemical study and research. 



That animals, such as the carnivora, in which digestion is a more or less 

 intermittent process, should always possess a gall-bladder is intelligible 

 enough, and that the exceptional cases in which this reservoir is absent 

 should occur, mainly, in the herbivora is on the whole intelligible. It is 

 impossible, however, to account for the exceptions, so far as the Author 

 knows, either on morphological or physiological grounds. Thus, whilst 

 oxen and sheep conform to the rule and have a gall-bladder, deer have 

 none. The solidungula are distinguished by absence of gall-bladder. 

 Whilst our domestic birds, in general, possess a gall-bladder, the pigeon 

 has none. The parrot and the ostrich, amongst well-known birds, also 

 have no gall-bladder. 



Whilst we are able, as has been said, to obtain, for chemical 

 study, bile from the gall-bladder of dead animals, it is impossible to 

 study the process of secretion, to determine its relations in point of 

 time to the various digestive acts, and to form adequate conceptions 

 of the part which it plays in the various digestive processes, unless 

 we supplement the facts ascertained in other ways by observing 

 animals in which biliary fistula? have been established. 



Establish- Schwann 1 was the first to establish biliary fistula?, 



ment of bill- and his method of operating has in general been imi- 

 ary flstuiae. tated by subsequent observers. 



The dog is the animal which has almost invariably been employed 

 when the object has been to make & permanent biliary fistula. Hav- 



1 Th. Schwann, Versuche um auszuraitteln ob die Galle im Organismus eine fiir 

 das Leben wesentliche Kolle spielt,' Archiv f. Anat. u. Phys. (1844), pp. 127159. 

 Although Schwann has the merit of having first established permanent biliary fistulae, 

 the dogs upon which he operated and which survived the immediate effects of the 

 operation died in two or three hours, and he was in consequence led to attach an 

 exaggerated and untrue importance to the part which the bile .plays in the economy. 

 Schwann employed no cannulae to collect the bile. So far as the Author knows it was 

 Blondlot who first did so in cases of biliary fistulae. 



