266 AN AMERICAN TEXT- HOOK OF PHYSIOLOGY. 



is eliminated from the body by the kidneys, but it is known not to be formed 

 in these organs. Modern investigations have seemed to show conclusively 

 that this substance is formed mainly within the liver from some ante- 

 cedent body (ammonia compound) which arises in the proteid tissues 

 generally, but is not prepared for final elimination until in the liver or else- 

 where it is converted into urea. Here again the liver-cells perform a metab- 

 olism for the good of the organism as a whole, and the act of passing out 

 the urea into the blood may be regarded as an internal secretion. It is quite 

 possible that in still other ways the liver-cells add to the blood elements of 

 importance to the tissues of the body — as, for example, in the conservation and 

 distribution of the iron of broken-down haemoglobin (see p. 323), or in the syn- 

 thetic combination of the products of putrefaction formed in the intestines (indol, 

 skatol, phenol, ete.) with sulphuric acid (see p. 340) ; but concerning these mat- 

 ters our knowledge is not yet sufficiently definite to make positive statements. 

 Pancreas. — The importance of the external secretion, the pancreatic juice, 

 of the pancreas has long been recognized, but it was not until 1889 that von 

 Mehring 1 and Minkowski proved that it furnishes also an equally important 

 internal secretion. These observers succeeded in extirpating the entire pan- 

 creas without causing the immediate death of the animal, and found that in 

 all eases this operation was followed by the appearance of sugar in the urine 

 in considerable quantities. Further observations of their own and other experi- 

 menters ' have corroborated this result and added a number of interesting facts 

 to our knowledge of this side of the activity of the pancreas. It has been 

 shown that when the pancreas is completely removed a condition of glycosuria 

 inevitably follows, even if carbohydrate food is excluded from the diet. More- 

 over, as in the similar pathological condition of glycosuria or diabetes mellitus 

 in man, there is an increase in the quantity of urine (polyuria) and of urea, 

 and an abnormal thirst and hunger. Acetone also is present in the urine. 

 These symptoms in cases of complete extirpation of the pancreas are followed 

 by emaciation and muscular weakness, which finally end in death in two to 

 four weeks. If the pancreas is incompletely removed, the glycosuria may be 

 serious, or slight and transient, or absent altogether, depending upon the 

 amount of pancreatic tissue left. According to the experiments of von 

 Mehring and Minkowski on dogs, a residue of one-fourth to one-fifth of the 

 gland is sufficient to prevent the appearance of sugar in the urine, although 

 a smaller fragment may suffice apparently if its physiological condition' is 

 favorable. The portion of pancreas left in the body may suffice to prevent 

 glycosuria, partly or completely, even though its connection with the duo- 

 denum is entirely interrupted, thus indicating that the suppression of the 

 pancreatic juice is not responsible for the glycosuria. The same fact is shown 

 more conclusively by the following experiments: Glycosuria after complete 

 removal of the pancreas from its normal connections may be prevented par- 



1 Archivfur exper. Pathologve and Pharmakologie, 1 >90, Bd. xxvi. S. 371. See also Minkow- 

 ski, Ibid., 1S93, Bd. xxxi. S. 85, for a more complete account. 



'See IIe\lon : Diab&te pancriatique, Travaux de Physiologie Universite de MontpeUier, 1898. 



