PHYSIOLOGY. 



the respiratory muscles are, however, ne- 

 cessary to the production of this effect. 



Although the stomach belongs to those 

 organs whose action is independent of the 

 will, and goes on, therefore, without the 

 attraction of the individual, yet it is so far 

 influenced by the brain, that the section of 

 its nerves entirely obstructs digestion. It 

 sympathises most remarkably both with 

 the constitution at large, and with parti- 

 cular organs. 



The chyme, or semifluid substance, in. 

 to which the action of the stomach reduces 

 the food, is propelled by the muscular 

 power of that bag into the duodenum, 

 where it undergoes new changes, particu- 

 larly from the admixture of other animal 

 fluids, the bile and pancreatic juice: and 

 this process is termed chylification. 



The secretion of the pancreas seems to 

 bear a considerable analogy, both in its 

 nature and office, to the saliva and gas- 

 tric juice. It is very difficult to procure 

 it in a pure and unmixed state from a 

 healthy animal, but the facts which we 

 hitherto possess, shew, that its properties 

 are very like those of saliva. It is poured 

 into the duodenum by the contractile pow- 

 er of the pancreatic duct : and its secre- 

 tion, like that of the salivary glands, is 

 said to be promoted by the pressure of 

 the stomach in its filled state ; and by the 

 stimulus <>t the chyme and bile on the ori- 

 fice of its duct. 



The bile is the fluid furnished by the 

 liver, the largest viscus of the human 

 body, whose importance in the animal 

 economy is evinced by its large apparatus 

 and complicated distribution of blood- 

 vessels, as well as by its constantly exist- 

 ing in all animals which have a heart. 



The source of the bile has been ques- 

 tioned, whether it be secreted from the 

 hepatic artery, or vena portarum ? The 

 analogy of other secretions, which are all 

 made from arteries, favours the former 

 opinion ; but the blood of the vena porta- 

 rum seems to be the fittest, from its na- 

 ture, for the secretion of bile. The hepa- 

 tic artery probably serves to nourish the 

 liver, as the lungs are nourished by the 

 bronchial artery. The distribution of the 

 vena portarum is like that of an artery. 

 If we suppose the hepatic artery to furnish 

 the bile, the excretory duct would be dis- 

 proportionately large. 



The bile, when secreted, passes by a 

 slow but constant stream through the he- 

 patic duct; but a greater or less pro- 

 portion is conveyed by the cystic duct into 

 the gall-bladder, in which it is accumu- 

 lated, as in a reservoir, and undergoes 



certain changes of properties, which make 

 it cystic bile. The biliary fluid probably 

 flows directly into the intestine, while the 

 assimilation of the food is going on ; and, 

 when the empty state of the duodenum 

 causes the end of the ductus communis 

 choledochus to be compressed by its mus- 

 cular coat, it regurgitates into the gall- 

 bladder. 



There is no direct communication be- 

 tween the liver and gall-bladder, and con- 

 sequently no other way for the bile to en- 

 ter that bag, except by the cystic duct. 

 The hepatic bile is a thin fluid, of a clear 

 orange colour, and slightly bitter ; the 

 cystic is viscid and tenacious, intensely 

 bitter, and very dark coloured. The bile, 

 thus changed by its residence in the gall- 

 bladder, is expelled by the contractile 

 powers of the gall-bladder and cystic duct 

 into the ductus communis, and thence 

 passes to the duodenum. This bladder 

 absorbs the watery parts of the hepatic 

 bile, and adds a mucous secretion to it. 



The chemical analysis, and theses of 

 the bile, are considered under that article. 



Function of the Spleen. The situation 

 and attachments of this organ lead us to 

 suppose, that its uses are in some way- 

 connected with the functions of the sto- 

 mach ; yet there is nothing more than 

 conjecture to be offered on this subject. 

 The removal of the part has been per- 

 formed in dogs without any material in- 

 jury to the animal. Its site differs, ac- 

 cording the quantity of blood contained in 

 its cells. Physiologists have stated, that 

 its blood possesses peculiar properties ; 

 that it is more fluid, does not coagulate, 

 nor separate readily into serum and eras- 

 samentum ; is more livid, and possesses 

 a greater quantity of carbon. As this 

 blood goes to the liver, and as the part 

 possesses no excretory duct, it has been 

 argued, that its function is subservient to 

 that of the liver, in imparting to the blood 

 those properties which fit it for the secre- 

 tion of bile. 



By others, the spleen has been regard- 

 ed as a sponge, swelling with blood when 

 the stomach is empty, and squeezed out 

 by the pressure of the stomach when that 

 organ is full. Thus, it is said, more blood 

 will go into the stomachic arteries when 

 the secretion of the gastric juice is going 

 on, and the superfluous part in the inac- 

 tive state of the stomach will distend the 

 spleen. 



Action of the small Intestines. The chyle, 

 formed in the duodenum, passes through 

 the tube of the small intestine, which is 

 the organ for absorbing its nutritive parts. 



