684 THE SEAT OF FORMATION OF UREA 



hepatic artery or to remove the liver. They found that removal 

 of the liver caused the death of the animal within a very few 

 hours. After ligature of the hepatic artery most of the dogs 

 died within fifteen hours, and it is possible that these lived so 

 long only because some collateral circulation had been set up in 

 the interval between the two operations. Owing to the unsatis- 

 factory results of their first series of experiments, Nencki and 

 Pawlow carried out a further series, but with no better result 

 to the duration of life. One dog after ligature of the hepatic 

 artery in addition to an Eck's fistula lived ten hours. After 

 the operation, the blood contained the same percentage of 

 urea and ammonia as before it ; the urine still contained 4'1 per 

 cent, of urea, and the urea formed the same percentage of the 

 total urinary nitrogen as before the operation. They estimated 

 the urea by SchondorfTs method. From these results they 

 concluded that the liver cannot be the only tissue which pro- 

 duces urea. These experiments cannot be considered con- 

 clusive. For ligature of the hepatic artery in addition to an 

 Eck's fistula does not necessarily put the liver wholly out of 

 the circulation ; a certain amount of collateral circulation may 

 still be possible through the liver, and this has been found to 

 vary in degree in individual dogs. The only conclusive method 

 could be the more serious operation of complete removal of 

 the liver. The most recent and successful attempts to carry 

 out this operation have been made by Salaskin and Zaleski. 

 Their method was to make an Eck's fistula, ligature the portal 

 vein between the fistula and the liver, and then ligature off 

 the liver bit by bit. Their most successful result was in a 

 dog which lived 13 hours after the operation. Previously the 

 dog had been starved for 10 days. For 8J hours after the 

 operation the dog remained in fairly good condition and had 

 a blood pressure of 100 mm. Hg. At 10 1 hours tetaniform 

 convulsions started and lasted until death. The total urine 

 passed subsequent to the operation was 118'5 c.c., of which 

 nearly the whole was passed within the first 8 hours. It con- 

 tained lactic acid and 4 grm. of urea in all. The urea-N fell 

 from 89 per cent, to 70 per cent, of the total N, and the 

 ammonia-N rose from 3'5 per cent, to 15*5 per cent, of the 

 total N. In this experiment the urea was estimated by Schon- 

 dorffs method, but in others it was estimated by the Morner- 



