PRODUCTION OF SUGAR IN THE LIVER. 303 



test is that, when it is altered so as to be unreliable, the 

 yellow precipitate is thrown down by simple boiling. In 

 making delicate examinations, it is best always, when this 

 occurs, to make a fresh solution. 1 



Examination of the Blood of the Portal System for 

 Sugar. If starch or sugar be taken into the alimentary 

 canal, it is well known that sugar is always to be found, 

 during absorption, in the blood of the portal system ; but 

 in the carnivorous animals, that have been fed entirely upon 

 meat, no sugar is to be found in the portal blood. Bernard 

 is very definite upon this point, and indicates a liability to 

 error when the operation of tying the portal vein has not 

 been skilfully performed, and when blood, containing sugar, 

 is allowed to regurgitate from the substance of the liver. In 

 taking the blood just before it enters the liver, it is necessary 

 to apply a ligature to the vessels as they penetrate at the 

 transverse fissure. This should be done quickly, and the 

 opening into the abdominal cavity should be small. Other- 

 wise, as the vessels have no valves, we are liable to have re- 

 flux of blood from the liver. We have frequently performed 

 the experiment, after the method described by Bernard, 

 making a small opening in the linea alba a little below the 

 ensiform cartilage, just large enough to admit the forefinger 

 of the left hand ; introducing the finger, and feeling along 

 the concave surface of the liver until we are able to seize 

 the vessels; then passing in an aneurism-needle, and con- 

 stricting the vessels before the abdomen is widely opened^ 

 when a firm ligature is applied. When this step of the 

 operation has been satisfactorily performed, we have never 

 found a trace of sugar in the extract from the blood of the 

 portal system, in animals that have been fed upon nitrogen- 

 ized matter alone. 



Among those who have refused to admit the glycogenic 



1 The properties of the test-liquid may be restored sufficiently for ordinary 

 qualitative examinations by adding a little more caustic soda and filtering. 



