746 SPECIAL PHYSIOLOGY. 



pancreatin, this ferment might be some albuminoid product of one of 

 the ductless glands ; but extirpation of the salivary glands or pancreas, 

 of the spleen, suprarenal bodies, thyroid, or thymus, in a series of ex- 

 periments on animals, threw no light on the question. (Schiff.) The 

 albuminoid substance is probably formed in the liver itself; for, 

 whereas glycogen, like starch or dextrin, is not easily transmissible 

 through the coats of the hepatic vessels, it is probably converted into 

 the readily dialyzable sugar, before it is taken up by those veins. 

 The fibrin and albumen of the blood, whether arterial or portal, will 

 also convert dissolved glycogen into sugar. A boiling temperature 

 destroys the power of the ferment, whatever this may be. 



It has been suggested by Pavy that, although an amyloid substance 

 abounds in the liver during life, no sugar, or but very small traces of 

 it, are then present in this organ ; and that, except in disease, trans- 

 formation of the hepatin into sugar is, for the most part, a post-mor- 

 tem result. This observer found no great difference in the quantity of 

 sugar in the various large bloodvessels, either in the arteries, or in the 

 hepatic or portal veins; the quantity detected was very small, aver- 

 aging about y gth of a grain in 100 grains of blood. In the liver-sub- 

 stance itself, macerated, instantly after death, in caustic potash or in 

 very cold water, no sugar could be detected, though the hepatin or 

 glycogen was then extracted. Most physiologists, however, coincide 

 with Bernard, in believing that the formation of sugar in the liver 

 is constantly taking place during life ; and that the accompanying 

 decomposition of the glycogen into sugar may explain the relative 

 higher temperature of the blood which has been observed in the he- 

 patic veins. 



The average quantity of sugar obtainable from the liver of the horse 

 and calf, varies from 4 to 2 per *cent. ; in the rabbit's liver, it is about 

 2.5 per cent., and in Man, as noticed in healthy, recently executed 

 criminals, about 2 per cent. (Bernard.) By others, sugar has been 

 found in the liver of Birds, Reptiles, and Fishes, though in the cold- 

 blooded animals the quantity is small ; it has even been detected in 

 the liver of the Mollusca. (Bernard.) It is more easily obtained from 

 the veins than from the substance of the organ. The relative propor- 

 tion found in the portal blood, in the systemic venous blood, and in 

 the arterial blood of animals fasting, or fed only on flesh, is about .06 

 parts in 100 ; whereas, in the hepatic blood, the quantity is usually 

 about 1 per cent. In fully fed animals, especially after a meal con- 

 taining starch, the quantity in each kind of blood is increased. In one 

 experiment on a well-fed horse, killed soon after digestion, the pro- 

 portion of sugar found in the liver was nearly 2.3 per cent.; whilst 

 that in the hepatic vein was about 1.1, in the lymph .44, in the chyle 

 .22, and in the blood generally .065. (Poiseuille and Lefort.) 



The glycogen of the liver being admitted to be the source of the 

 sugar found in the hepatic blood, the origin of the glycogen itself is 

 yet undecided. Some have questioned the power of animal tissues to 

 form an amyloid substance, and have suggested that the glycogen of 

 the liver is derived from the starchy matter of the food, which might 

 be supposed, in Herbivorous animals, to be partly accumulated, in a 



