NORMAL ANATOMY OF THE LIVER. 



180 



developed by the progressive discoveries of our 

 improving science, conclude that the bile is 

 secretcdfrom venous blood 1 



The quantity of the bile is a question diffi- 

 cult to decide accurately ; it would appear to 

 be secreted most abundantly during digestion, 

 when the augmented activity of the stomach 

 would seem to be communicated to its neigh- 

 bouring organ, the liver. Certainly it is eva- 

 cuated from the gall-bladder into the digestive 

 canal at that period. In animals which have 

 been kept long fasting the gall-bladder is always 

 greatly distended. Schultz observed, in an ox 

 which had been kept for some time without 

 food, from twelve to sixteen ounces of bile in 

 the gall-bladder, and in another, after digestion, 

 from two to four ounces only. In a dog which 

 had not eaten for some time he found five 

 drachms, in another, after digestion, about two 

 drachms. In a case of abscess of the liver 

 communicating with the gall-bladder and 

 lung, recorded by Dr. Monro, the whole 

 of the bile flowed through the fistulous canal 

 and was discharged by coughing, " in proof of 

 which," he says, " the faeces were of the same 

 whitish colour and had as little smell as those 

 of a person deeply jaundiced. The quantity 

 of bile discharged by coughing was different at 

 different times. It was always greater after 

 meals, and especially for an hour or two after 

 dinner. The quantity expectorated could not 

 be measured with great accuracy from being 

 mixed with mucus and saliva. The whole 

 quantity in twenty-four hours was from ten to 

 fifteen ounces; and, in this case, I had an 

 opportunity of observing the effects of certain 

 articles of food, and in particular of acids, of 

 wine, and of different fruits, in increasing the 

 quantity of bile." 



Expulsion of the bile. This process 1 have 

 just shewn takes place more abundantly during 

 digestion than at any other period. In all 

 carnivorous and in most herbivorous animals 

 there exists a peculiar provision for the col- 

 lection of the bile during the period of ab- 

 stinence, in a membranous reservoir, the gall- 

 bladder. Some herbivorous animals, deprived 

 o.' a distinct gall-bladder, have a compensating 

 dilatation upon the hepatic duct. The use of 

 this organ is to retain the bile until digestion 

 demands its excretion. Those animals, there- 

 fore, that are provided with it are such as 

 perform the function of digestion at variable 

 intervals. But in those whose digestion is con- 

 tinuous, as is the case in many herbivora, the 

 bile flows as it is secreted into the alimentary 

 canal ; being very probably provided more 

 abundantly under the stimulus of a full sto- 

 mach than during the abstinence from food or 

 during sleep. In the contracted state of the 

 duodenum the small and oblique opening of 

 the ductus communis choledochus is closed to 

 the passage of the fluid ; it therefore regurgitates 

 along the cystic duct into the gall-bladder. Jn 

 tlie slight ascent along this tube it is facilitated 

 by the spiral valve, which also serves to restrain 

 its too sudden emission during spasmodic ac- 

 tion of the abdominal muscles. As soon as 

 the duodenum becomes filled with the chyme 

 from the stomach, the opening of the ductus 



communis choledochus is less compressed. The 

 distension of the stomach, but more particu- 

 larly the passage of the chyme along the py- 

 lorus into the upper part of the duodenum, 

 causes a gentle pressure upon the coats of the 

 gall-bladder which favours its emission; its 

 contents are gradually expressed, and flowing 

 along the ductus communis choledochus are 

 mingled with the pulpy mass in the duodenum. 

 This explanation of the process seems to have 

 been entertained by Ilaller, and to have arisen 

 in his mind from the consideration of the ana- 

 tomy of the serpent, where the gall-bladder is 

 far removed from the liver and is situated in 

 the space formed by the contraction of the py- 

 lorus and its termination in the small intes- 

 tine. Neither do I consider its truth invali- 

 dated by those cases in which the gall-bladder 

 is partly imbedded in the liver, for in such 

 instances that portion of the liver is compressed 

 which immediately covers the fundus of the 

 gall-bladder, or a part of the gall-bladder is 

 exposed against which the duodenum may 

 exert an equal compression. Miiller conceives 

 that the efferent ducts of glands are surrounded 

 by " an extremely thin layer of muscular sub- 

 stance," which, although not demonstrable ana- 

 tomically, he thinks to be placed beyond dispute 

 by physiological observations. " The contractile 

 power of the ductus choledochus in birds was 

 known to Rudolphi. By irritating mechanically 

 or by galvanism the ductus choledochus of a 

 bird just dead, I have frequently produced a 

 very strong contraction of it, which continued 

 some minutes, after which the duct resumed 

 its previous state. I have often excited strong 

 local contractions of the ureters likewise, both 

 in birds and rabbits, by the application of a 

 powerful galvanic stimulus. Tiedemann also 

 has seen motions of the vas deferens of a horse 

 ensue on the application of a stimulus. It 

 appears indeed that periodic vermicular motions 

 are performed by the efferent ducts, at least by 

 the ductus choledociius, in birds ; for I have 

 once observed in a bird just killed, contractions 

 of the duct occurring regularly in pauses of 

 several minutes, the tube dilating again in the 

 intervals ; and what was remarkable, the con- 

 tractions took place in an ascending direction, 

 namely, from the intestine towards the liver : 

 and this seems to throw some light on the 

 mode in which the bile at certain times, in- 

 stead of being expelled into the intestines, is 

 retained and driven into the diverticulum of 

 the duct, namely, the gall-bladder ; the com- 

 pltte closure of the mouth of the duct contri- 

 butes perhaps to this effect. The discharge of 

 the bile from the gall-bladder during digestion 

 results probably from the mere pressure of the 

 surrounding parts, and the action of the ab- 

 dominal muscles, while the mouth of the duct 

 is open : for I doubt if the gail-bladder is con- 

 tractile ; I could produce no contraction of it 

 in mammalia and birds even with the most 

 powerful stimulus of a galvanic battery." Dr. 

 Monro considers the middle coat of the gall- 

 bladder in man to contain muscular fibres ; the 

 muscular coat in the gall-ducts of the dog and 

 hor.^e are, he observes, quite distinct, and upon 

 irritation he has seen the gall-bladder contract 



