ON THE BRITISH ANNELIDA. 221 



to the bile of serpents. The observations of Strecker further show, that in 

 the case of the dog, the nature of the food exercises no influence on the 

 composition of the bile. Sheep's bile contains a great preponderance of 

 taurocholate over glycocholate of soda ; while the bile of the goose, accord- 

 ing to Marson, contains scarcely anything but taurocholic acid. 



This tendency to variation occurs even in the colouring elements of the 

 bile. The characteristic bile-pigment is present in all classes of animals ; in 

 the Carnivora and Omnivora, including Man, it is brown in colour — the cho- 

 lepyrrhin of Berzelius ; while in Birds, Fishes and Amphibia, the same bile is 

 intensely green in colour — the biliverdin of the chemist. The cholepyrrhin is 

 always combined with soda or lime ; most commonly with the former. These 

 two varieties of biliary pigments will be found in the Annelids. In most 

 animals, the bile of which has been hitherto examined, the taurocholate of 

 soda is the principal constituent. 



In every kind of bile there exist invariably two essential constituents, namely, 

 the resinoid and the colouring element ; the resinoid constituent is the soda- 

 salt of one of the conjugate acids (glycocholic and taurocholic), having either 

 glycine or taurine for its adjunct. Another extraordinary fact very recently 

 established by Bensch, and confirmed by Strecker, may here be mentioned, 

 to illustrate the observation that the same function may be discharged in 

 different animals by a secretion which exhibits as many special diversities in 

 composition as the organ by which it is formed varies morphologically. 

 This fact is, that the bile of salt-water fishes consists almost entirely of potash- 

 salts, while that of the herbivorous mammalia consists almost entirely of 

 soda-salts, the very reverse of that which the chemist would have antici- 

 pated. Thus, then, in terms in common use in physiology, implying an es- 

 sential unity of idea, particulars, essentially diverse, are utterly lost. In the 

 invertebrate animals fat-cells constitute the chief morphological elements of 

 the bile. There can be no doubt that between fat and bile, in the lower 

 invertebrata especially, there obtains an intimate relationship. In the biliary 

 glandules of the Annelida, Crustacea and Echinodermata, all that is visible 

 consists only of oil-cells. Whatever be the real office discharged by these 

 oleaginous principles, observation, chemical and microscopic, proves that they 

 exist also in the higher animals. The proportion of fatty matter which (for 

 instance, in man) is contained in the blood of the portal vein, is to that in 

 the blood of the hepatic vein as 3*225 is to 1*885. It is supposed by Schmidt, 

 that the oily matter brought to the biliary organ by the blood, resolves itself 

 into sugar and water on the one hand, and into cholic acid and water on the 

 other ; the two constituents of cholic acid, glycerine and oleic acid, with 

 certain proportions of oxygen, being equivalent to sugar and cholic acid. It 

 may be at present affirmed as most probable, that the essential agency of the 

 ultimate hepatic cells results in the production out of the blood of sugar and 

 cholic acid, the former being eliminated by the hepatic veins, while the latter 

 remains in the secretion, and may be regarded as bearing to the bile the same 

 essential relation as that which exists Ijetween the urea and the urine. It 

 must now be clear that the action of the bile on the contents of the aliment- 

 ary tube must vary with the' differences of chemical composition exhibited 

 by this secretion. This must also be the case with reference to other organic 

 secretions. The true gastric juice of the Annelid, however, or wherever 

 secreted, may, for example, diff'er in many striking respects from that of man, 

 and yet it may enact a part in the process of digestion essentially correspond- 

 ent to that of which the human stomach (not the moutK) is the scene. There 

 remains, however, another general proposition with reference to the chemistry 

 of the fluids in the inferior animals which should be enounced with precision 



