340 DIGESTION. 



to subserve some purpose in relation to the formation 

 of fat. 



For the present we must remain uncertain as to which 

 of these theories contains most truth in it. It is right, 

 however, to remark that experiments made by Dr. Thudi- 

 chum, and by Dr. Harley, with Dr. Sharpey's co-operation, 

 tend to invalidate the conclusions to which Dr. Pavy has 

 been led. 



"Whatever be the destination of this peculiar amyloid 

 substance formed at the liver, most recent observers agree 

 that it is formed at, and exists within, the hepatic cells, 

 from which it may be readily extracted by boiling, and 

 then separated from the decoction by the addition of 

 alcohol, which at once precipitates it. When isolated and 

 purified it is said to be whitish, tasteless, soluble in water, 

 and to possess the chemical qualities intermediate between 

 those of hydrated starch and dextrin. Its composition is 

 C 12 H 10 10 . It manifests, as already observed, a remark- 

 able tendency to pass into sugar in presence of any animal 

 ferment, such, for example, as may be found in the blood, 

 urine, saliva, or pancreatic secretion. Whether this be its 

 natural destination is, however, still an open question. 



Much doubt exists also respecting the mode in which 

 this glycogenic or amyloid substance is formed in the liver, 

 and the materials which furnish its source. Since its 

 quantity is increased after feeding, especially on substances 

 containing much sugar or starch, it is probable that part 

 of it is derived from saccharine principles absorbed from 

 the digestive canal ; but since its formation continues even 

 when there is no starch or sugar in the food, the albumin- 

 ous or fatty principles also have been thought capable of 

 furnishing part of it. Numerous experiments, however, 

 having proved that the liver continues to form sugar in 

 animals after prolonged starvation, and during hybernation, 

 and even after death, its production is clearly independent 

 of the elements of food. One of Bernard's experiments 



