staying too long at the job without suitable rest periods. The regulations 

 required also a full day of rest in seven, and vacation periods as well as 

 adequate time allowances for lunch. Excessive work schedules were found 

 to reduce the flow of production as well as to impair the health and effi- 

 ciency of the workers. 



In Brief 



Among the substances produced in living things during metabolism, 

 some are useless or even injurious to the protoplasm. 



Plants eliminate carbon dioxide and water, but usually accumulate other 

 wastes in insoluble combinations in various tissues, where they do not inter- 

 fere with vital activities. Animals deposit wastes in special tissues of the 

 body to a slight extent. 



In the higher animals wastes are diffused into the blood and removed 

 from the body by special organs, such as sweat glands and kidneys, or by 

 the intestines. 



In the vertebrates, nitrogenous and other wastes are removed from the 

 blood by the two bean-shaped kidneys. 



Each kidney consists of a mass of tiny tubules interwoven with a com- 

 plex network of capillaries. The wastes diffuse from the blood into the 

 tubules, from which they are discharged from the body as urine. 



The urine, which is about 96 per cent water, contains dissolved substances 

 resulting from the breakdown of proteins during metabolism. 



The composition and concentration of the urine are constantly changing. 



11. J lllMllillllliillllMIIIIII IIIIIIMIIIlllllMllillinllll:-'! 



THE PACE THAT TIRES 



,1 hlullllllllllNIII IlllllllllllllJllllllHIHIlllllllllllHIIllllllllllllllllI IIIM IIIIIIIIIIIIIIIIIIII I IIIIIIIMIIUliKUmXl->-''VMlimJllll. 



These two ergograph records were made by the some student. The first he made by 

 pulling as rapidly as he could and as far as he could: this shows fatigue coming 

 on rapidly. The second was made by a slow, steady pull, taking two seconds each 

 time. Although the action continued twice as long in the second case and the actual 

 work performed was about four times as much, there is hardly any evidence of fatigue 



225 



