METABOLISM, NUTRITION AND DIETETICS 517 



It has been asserted that the blood which leaves even a resting 

 muscle, or an inactive salivary gland, is poorer in sugar than 

 that coming to it ; and the conclusion has been drawn that in 

 the metabolism of resting muscle and gland sugar is oxidized, 

 the carbon passing off as carbon dioxide in the venous blood. 

 This is indeed extremely likely, for we know that when the 

 skeletal muscles of a rabbit or guinea-pig are cut off from the 

 central nervous system by curara, the production of carbon 

 dioxide falls much below that of an intact animal at rest ; and 

 the carbon given off by such an animal on its ordinary vegetable 

 diet can be shown, by a comparison of the chemical composition 

 of the food and the excreta, to come largely from carbo-hydrates. 

 But, considering the relatively feeble metabolism of muscles 

 and glands when not functionally excited, the large volume of 

 blood which passes through them, the difficulty of determining 

 small differences in the proportion of sugar in such a liquid, the 

 possibility that even in the blood itself sugar may be destroyed, 

 or that it may pass from the blood, without being oxidized, 

 into the lymph, too much weight may be easily given to the 

 results of direct analysis of the in-coming and out-going blood. 

 And although the results of Chauveau and Kaufmann, obtained 

 in this way, fit in fairly well with what we have already learnt 

 by less direct, but more trustworthy, methods, they cannot be 

 accepted as yielding exact quantitative information. They 

 found that in one of the muscles of the upper lip of the horse the 

 quantity of dextrose used up during activity (feeding movements) 

 was 3 '5 times as much as in the same muscle at rest, and this 

 corresponded with the deficit of oxygen in the blood entering the 

 muscle, and with the excess of carbon dioxide in the blood leaving 

 it. More dextrose was also destroyed in the active than in the 

 passive parotid gland of the horse, but the excess per unit of 

 weight of the organ was far less than in muscle. 



Concerning the manner in which dextrose is destroyed in the 

 tissues, we are in the same position as in the case of the proteins. 

 It cannot be definitely stated at present what share is taken by 

 cleavage and what by oxidation in the destruction of carbo- 

 hydrates in the organism, although oxidation is known to play an 

 important role. Normal blood has been credited with a ferment 

 which has the power of destroying sugar (glycolysis) . But with 

 rigid aseptic precautions the loss of sugar, even in several hours, is 

 small, and it is doubtful whether such a ferment exists. On the 

 other hand, Cohnheim stated that while no glycolytic ferment can 

 be demonstrated in the pancreas, and only an exceedingly weak 

 glycolytic action in muscular tissue (Brunton), by combining 

 pancreas and muscles distinct glycolysis, due to a ferment action, 

 could be produced. He suggested that the glycolytic ferment is 



