208 MAKUAL OF OATTLE-B^EKDIXG. 



These results show, first, that the decompositions, hoth 

 of protein and of non-nitrogenous matters, going on in the 

 body are more active during the waking hours than at 

 night, a fact which has been abundantly confirmed by 

 other observations ; and second, that the performance of 

 muscular work during the day has practically no eftect on 

 the extent of the protein consumption, while it largely in- 

 creases the amount of carbonic acid and water exhaled 

 dm-ing the day. 



That muscular exertion causes an increased excretion of 

 carbonic acid and water is universally acknowledged ; but, 

 in spite of the decisive results of Pettenkofer & Voit, and 

 the corroborative results of various other investigators, the 

 fact of the constancy of the nitrogen excretion under the 

 influence of woi'k has been disputed. 



Excretion of Gaseous NitrogeD, — That under ordi- 

 nary circumstances no excretion of free nitrogen from the 

 body takes place has been already shown ; but it has been 

 sometimes claimed that in severe work a portion of the 

 nitrogen coming from the destruction of the albuminoids 

 is excreted* in the gaseous form through skin and lungs, 

 and that consequently the protein consumption cannot be 

 calculated from the urinary nitrogen. According to this, 

 the close agreement observed in the above and many other 

 experiments between the urinary nitrogen on the days of 

 rest and work is entirely accidental — ^a thing which is cer- 

 tainly very improbable of itself, and which is disproved by 

 the following considerations and experimental results. 



If, in consequence of work, the total protein consump- 

 tion is considerably increased, there must be a coiTespond- 

 iiigly increased excretion of sulphuric and phosphoric acids 

 in the urine ; for with every portion of albunn'noid tissue 

 destroyed, the sulphur and phobphorus which it contains 



