236 THE POPULAR SCIENCE MONTHLY. 



many bad smells which, /)er se, though very disagreeable, have no 

 marked poisonous action, while other very poisonous substances have 

 comparatively little odor.* Yet the disagreeable odors which accom- 

 pany sewer-gas, although perhaps not always dependent upon its 

 poisonous constituents, warn us of the presence of gases which may 

 be intensely poisonous. Nevertheless, just as the poisonous gases 

 may be present without any disagreeable smell,, so we may have 

 substances circulating in the blood which have the most injurious 

 effect upon the nerve-centers, without the presence of urates in the 

 urine. 



The importance of the functions of the liver in reference to assimi- 

 lation is now generally recognized, although for a long time this, the 

 largest gland in the body, was considered to have no other office than 

 simply to secrete bile. Although the bile is useful in digestion it is not 

 of primary importance in this process ; but its proper secretion is prob- 

 ably associated very closely with the assimilative functions of the liver, 

 and if the biliary secretion does not take place properly we can hardly 

 expect the assimilation to be perfect. 



The greatest care appears to have been taken in the construction 

 of the liver to prevent the bile from coming in contact with the blood, 

 the ultimate radicals of the bile-ducts or biliary capillaries being placed 

 as far from the blood capillaries as the structure of the liver will allow. 

 Notwithstanding this care, the distance between the blood and the bile 

 capillaries is small, though it is sufficient, under ordinary circumstances, 

 to prevent the absorption of bile into the blood. But whenever an ob- 

 struction takes place to the exit of bile, and the presence of bile in the 

 biliary capillaries increases, an absorption of this secretion occurs. Bile 

 is secreted under very low pressure, and a very slight increase in this is 

 sufficient to cause reabsorption. Such an increase as would not materi- 

 ally affect the secretion of other glands, such as the salivary gland, is 

 sufficient to prevent the exit of bile through the biliary ducts, and cause 

 its reabsorption into the blood. The excretion of bile is greatly aided 

 by the pressure which is exerted upon it by the movements of the dia- 

 phragm during respiration, and indeed so low is the pressure under 

 which the bile is secreted that, but for the assistance given by the re- 

 spiratory movement, it would just barely find its way into the duode- 

 num. Although we are accustomed to say " as bitter as gall," accord- 

 ing to my own observations fresh human bile is not bitter. When it is 

 thrown up in consequence of indigestion it is intensely bitter. On one 

 occasion, when making experiments with digitalis, I had taken in the 

 course of two days one grain of the pure alkaloid, and brought on symp- 

 toms of poisoning, with intense vomiting. During this I brought up 

 a quantity of bile of a golden-yellow color, and without the least trace 

 of bitterness. This circumstance struck me as being so peculiar that 

 in my published results I hesitated to call it bile, although I did not 

 * Brunton and Power, "St. Bartholomew's Hospital Reports," 19,11, p. 283. 



