METABOLISM IN NEUROMUSCULAR DISEASES T15 



fixed quantities determined by the amounts of carbohydrate, protein, and 

 fat oxidized. A diminution in the oxygen supply, resulting from asthma, 

 heart disease, anemia, and similar conditions, does not affect the oxygen 

 consumption, o>r carbon dioxid production required to develop a certain 

 amount of energy. If the work is done, the gaseous exchange is unaffected. 

 The result of a restriction in the oxygen supply is a diminution of the 

 amount of work that can be done. The striking symptom, common to 

 asthma, heart disease, anemia, high altitude sickness, and similar condi- 

 tions, is weakness. The food supply in these conditions may be adequate 

 to supply abundant energy, but the amount of fooH that can be utilized 

 is limited to that which can be oxidized to carbon dioxid and water, by the 

 oxygen available; and the oxygen available may be subnormal in quantity. 



THE SUPPLY OF GLUCOSE 



The same symptom, namely, muscular weakness, may result when the 

 food supply is inadequate, or when, though adequate, the muscles cannot 

 make use of it. Abstinence from food, in so far as its effect on muscular 

 activity is concerned, is analogous to the inadequate oxygen supply result- 

 ing from diminished external or internal respiration. But weakness be- 

 comes a prominent symptom of starvation only when the starvation is 

 rather extreme. Up to this point, compensatory processes mobilization 

 and transformation of material within the body maintain the immediate 

 source of muscular energy, blood sugar, at the normal level. 



But muscular weakness is a prominent symptom when the food supply 

 though adequate, cannot be utilized by the muscles. This is the case in 

 the paralyses resulting from pathological conditions in the central nervous 

 system and in curare poisoning. The food supply and the blood sugar may 

 be normal, but the muscles cannot utilize these materials to do mechanical 

 work. In severe diabetes the weakness is due to the inability of the tissues 

 to oxidize glucose. In phi or iz in diabetes, and in certain myopathies, the 

 weakness is due to disturbances of the carbohydrate metabolism, resulting 

 in inadequacy in the supply of the most immediate available source of 

 energy the blood sugar. Diabetes is discussed elsewhere in this work, 

 but the other conditions come within the scope of this article. 



Actively contracting muscle rapidly uses up glucose from the blood 

 passing through it. A contracting muscle may use up more than six 

 times as much as a resting muscle (Morat et Dufourt). The venous blood 

 leaving a faradized muscle may contain only half as much glucose as the 

 blood leaving a resting muscle (Quinquaud). Following severe muscular 

 activity, the amount of glucose used may be so great that the blood sugar 

 content of even the general circulation may fall (Broslauer, Chauveau et 

 Kaufman (6)). Weiland, using a Gartner ergostat, had six of his col- 

 leagues do severe muscular work, almost to the point of exhaustion, and 



