334 PHYSIOLOGY CHAP. 



which is due to an unknown capacity of conversion by the 

 hepatic cells. 



F. Schupfer, under Colasanti's directions, made equally 

 interesting observations on dehepatised as compared with normal 

 frogs, in regard to the toxicity of alkaloids inoculated beneath the 

 skin of the back. He was able to demonstrate that the liver 

 reduces the toxicity of cocaine hydrochlorate by -f ; of neutral 

 sulphate of atropine by about i ; of apomorphine hydrochlorate by | ; 

 of pilocarpine hydrochlorate by |. 



Many other experiments were made by other workers, with 

 the object of discovering whether, under conditions in which the 

 liver is unable to function properly, either in pathological states or 

 after operations, the toxicity of the urine increases abnormally. 

 The results of Eoger (1886), Surmont (1892), Bellati (1893), 

 Villetti (1893), Bisso (1895), tend to show that the toxicity of 

 urine is more or less proportional to the gravity of the anatomical 

 and functional lesions of the liver. 



Bisso's work, under the direction of Colasanti, seems the most 

 definite. He operated on dogs by gradual occlusion of the portal 

 system (Bernard-Ore method), collected the urine, and deter- 

 mined its toxicity by Bouchard's method of injection into the 

 veins of rabbits. 



He found that the toxicity of the urine varies in normal dogs 

 with the diet. It is maximal with a flesh diet, minimal with a 

 milk diet, intermediate on a diet rich in fats. After occlusion of 

 the portal vein, urinary toxicity is tripled, while the original 

 ratio between the several diets persists. The liver accordingly 

 functions as a protective organ in the body, by arresting and 

 destroying the toxic substances formed during the secretory, 

 digestive, and putrefactive processes of the alimentary canal. A 

 strict functional relation between the liver and kidneys must also 

 be admitted, since, when the protective function of the liver is 

 in abeyance owing to occlusion of the portal vein, the kidneys 

 function more actively, and expel the toxic substances accumulated 

 in the body. 



In order to define the nature of the protective function 

 normally exercised by the liver against the toxic products that 

 enter through the portal roots, Schroder and Salomon established 

 an artificial circulation in the liver, and made a chemical analysis 

 of the blood before and after it passed through this organ. They 

 saw that on adding ammonium carbonate to the blood, it was con- 

 verted into urea after circulating through the liver. This con- 

 version is due to a synthetic process effected by the hepatic cells, 

 in which the ammonium carbonate loses water and is converted 

 into urea. This conversion does not take place if the blood is 

 circulated through the kidneys or muscles. 



After excision or ligation of the liver in geese, Minkowski 



