PRODUCTION OF SUGAR IN THE LIVER. 323 



never passes the lungs, and does not exist in the arterial 

 system. During digestion, however, even when the diet is 

 entirely nitrogenized, the production of sugar is so much 

 increased that a small quantity frequently escapes decompo- 

 sition in the lungs, and passes into the arterial blood. 1 Un- 

 der these conditions, the quantity in the arterial blood is 

 sometimes so large that a trace may appear in the urine, as 

 a temporary and exceptional, but not an abnormal condition. 

 This physiological fact is well illustrated in certain cases of 

 diabetes. There are instances, indeed, in which the sugar 

 appears in the urine only during digestion ; a and in almost 

 all cases, the quantity of sugar eliminated is largely increased 

 after eating. Pavy mentions a very striking instance of this 

 kind, in which the examinations of the urine were made 

 with great care. 8 



The influence of the kind of food upon the glycogenie 

 function is a question of great pathological as well as physi- 

 ological importance. It is well known to pathologists that 

 certain cases of diabetes are relieved when the patient is 

 confined strictly to a diet containing neither saccharine nor 

 amylaceous principles,* and that, almost always, the quantity 

 of sugar discharged is very much diminished by such a course 

 of treatment ; but there are instances in which the discharge 

 of sugar continues, in spite of the most carefully-regulated 

 diet. Bernard does not recognize fully the influence of dif- 

 ferent kinds of food upon glycogenesis, and his experiments 

 on this point are wanting in accuracy, from the fact that the 

 proportion of sugar in the liver is given, without indicating 

 at what period after death the examinations were made. In 

 the observations on this point by Pavy, the examinations of 



1 BERNARD, Lefons de physiologic experimentale, Paris, 1855, p. 111. 



2 BERNARD, op. tit., p. 114. 



3 PAVY, Researches on the Nature and Treatment of Diabetes, London, 1862, 

 p. 142. 



4 Several very striking examples of this kind are given by Pavy (op. *., p. 

 107). 



