PATHOLOGICAL METABOLISM OF THE BLOOD 575 



workers agree, on the whole, with those of Bauer and of Jiirgensen, not- 

 withstanding the criticism to which the earlier experiments are subject 

 because of the shortness of the periods of observation, the crudeness of 

 the methods employed, and the failure to, take adequate account of the 

 amount and composition of the food taken. Thus Hawk, and Gies found 

 in well-nourished animals, in weight and nitrogen equilibrium, and fed 

 continuously on a diet of constant composition, a temporary increase in 

 the elimination of nitrogenous products in the urine. Similarly, Haskins 

 (a) noted a decided rise in the amount of total nitrogen excreted on the two 

 days following hemorrhage. Such a primary rise in nitrogen elimination 

 has been observed also by Kerr, Hurwitz and Whipple(a) (&) (c) in their 

 studies on the regeneration of the blood proteins. For a few days follow- 

 ing the shock of plasmapharesis, there was a primary rise in nitrogen 

 elimination. In some instances, the initial increase in nitrogen output 

 after bleeding may be followed by nitrogen retention (Fuchs). 



Buell(6) in a recent study of the effect of hemorrhage on nitrog- 

 enous excretion in the pig found that only where the nitrogen elimi- 

 nated represented endogenous metabolism, was there indication of an 

 increased output. This observation harmonizes well with the results of 

 experiments on fasting animals. The fact that hemorrhage results in 

 greater nitrogen elimination in fasting animals has been interpreted to 

 mean that after protein starvation, the cells themselves must furnish 

 much of the new material needed to restore the blood and keep its compo- 

 sition constant. Thus the increased autolysis of body tissue and the 

 greater activity of the blood-forming organs results in a correspondingly 

 greater excretion of the end-products of protein metabolism than is the 

 case when extracellular sources are drawn upon. 



Most of the metabolism experiments indicate, therefore, that after 

 bleeding there is a relatively slight and only temporary increase in nitrogen 

 elimination. The influences which may bring about this stimulation of 

 protein catabolism are probably numerous and complex. At least three 

 factors must play a part in the production of the effects noted. In the 

 first place, loss of blood, if considerable, must at once affect the nutrition 

 of the higher centers concerned in the chemical and physical regulation of 

 certain body functions; secondly, hemorrhage, by greatly stimulating 

 the activity of the blood-making organs, results in an increase of the normal 

 waste products of these organs; and lastly, loss of blood influences pro- 

 foundly the exchange of fluids between the blood and the tissue spaces. 

 It is not unlikely that the withdrawal of fluid from the tissue spaces 

 which occurs after hemorrhage, to replace the volume of the blood, leads 

 to the accumulation in it of abnormal amounts of waste products, 

 ammonia components, creatin, and purin bases, which are eliminated by 

 the kidneys. 



A considerable diversity of opinion prevails, however, as regards the 



