WORK 113 



The Influence of Work on General Metabolism. 



Bernstein (70) has found that work plays some part in the general 

 metabolism of protein, even if it have no marked action on the cata- 

 bolism of this substance. He found that there was quite a marked re- 

 tention of nitrogen if protein were fed during the period in which work 

 was being carried out He held that the nitrogenous metabolism on 

 a constant protein intake was alike both for rest and work, but that 

 there was a difference in the nature of the protein consumed in the 

 two conditions a difference in the amount of tissue and circulating 

 protein utilized in the nomenclature of Voit (or in the amount of old 

 and fresh organized protein in the terminology of Pfliiger). There 

 might be an increase in the amount of old organized protein broken 

 down, but so long as there was a supply of material available for the 

 formation of the new protein, there would be no variation in the out- 

 put of nitrogen. Hypertrophy of muscle due to activity takes place 

 more freely when the amount of material present for building purposes 

 is large. Von Noorden believes that part of the retention even under 

 these conditions may be in the form of an inert reserve protein. 



Why does Work have so Little Apparent Influence on the 

 Catabolism of Protein ? 



What explanation is to be offered for the apparent anomaly that 

 work, which presumably increases the metabolism of the tissues, 

 which are mainly composed of protein, is accompanied by but little 

 increase of nitrogenous waste products in the urine? Examination 

 of the muscle itself has shown certain differences after work. Thus, 

 Burian (80) and McLeod (273) have shown that the purine content 

 is altered, Brown and Cathcart (75) have shown that there is an 

 alteration in the creatine content, and Pekelharing and Van Hoogen- 

 huyze (325) have found that a chemical change takes place, after 

 stimulation, and in rigor mortis, which leads to the formation of crea- 

 tine in muscle tissue. It is a fundamental law in mechanics that 

 every piece of machinery wears with work and that the greatest 

 amount of wear takes place in those parts which are most frequently 

 in use, and where friction is greatest. It is distinctly interesting if 

 the tissues muscular tissue in particular which are most deeply 

 involved both at rest and at work do not obey this law. Are they to 



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