922 SPECIAL PHYSIOLOGY. 



motor power in the body. By determining the quantities of urea ex- 

 creted by the kidneys, under different circumstances of rest and labor, he 

 endeavors to ascertain the potential energy represented by the urea, 

 considered as a product of the decomposition of the albuminoid tissues. 

 The work of the body is classified, by him, into vital, mental, and 

 mechanical. These he supposes to be represented respectively, by the 

 daily excretion of 297, 217, and 136.5 grains, making a total of 650.5 

 grains of urea ; the total daily amount excreted by a person engaged 

 in very active bodily and mental work is, therefore, 650.5 grains. In 

 routine labor, he infers that 400 grains of urea are sufficient to repre- 

 sent the vital and mechanical work ; but, in higher work, he allows 

 533 grains of urea ; and regards 575 grains as the average for a 

 healthy actively engaged adult. As 1 part of urea represents 3.1 

 parts of dried albumen, this daily average quantity of urea, viz., 575 

 grains, represents 3.9 oz. of dry albuminoid food ; 400 grains, 2.8 oz. ; 

 and 650 grains, 4.3 oz. This quantity is thus apportioned by Haugh- 

 ton : for the vital work, 297 grains, representing 2 oz. of albumen ; 

 for the mental work, 217 grains, representing 1.4 oz. ; and for the 

 mechanical work, 136.5 grains, representing .9 oz. To raise these 

 quantities into the actual quantities of albuminoid food consumed, T J 5 th 

 more must be added, in each case, for the albumen eliminated, un- 

 changed, in the solid excreta. Then it will be seen that the quantity 

 of urea taken to represent the vital work, is more than equal to the 

 flesh-formers in the subsistence diet of Playfair. But the quantity 

 said to correspond with the external mechanical work is insufficient, 

 representing, even with an addition of y^th, less than 1 oz. of albumi- 

 noid food ; whilst the mechanical work of an active healthy adult 

 demands, according to Playfair, an extra quantity of 2.2 oz. of flesh- 

 formers beyond the subsistence diet. The large quantity allotted to 

 mental work is perhaps excessive, and may supply the deficiency ; for 

 the quantity of albumen corresponding with the total amount of urea 

 is 4.4 oz. ; this, with its superadded y^th, would more than equal the 

 full diet of Playfair, though it would not approach the 5.5 oz. diet of 

 the active, much less the 6.5 oz. of the hardworked, laborer. 



But the estimates of Haughton as to the quantity of urea excreted 

 daily under conditions of labor, are less than the quantities which have 

 been observed by others. The quantity in convalescence, and in cases 

 of starvation or hunger-cure, ranges from 263 to 300 grains ; the 

 average quantity in health appears to vary from 560 to 580 grains ; 

 and the quantity excreted daily, by hardworked laborers, has been 

 found to differ, according to their work and/ood, from 600 to 700 or 

 800 grains. In Hammond's experiments on himself, whilst without 

 exercise, the quantity of urea excreted daily was 487 grains, and of 

 uric acid 24.9 grains, the quantities of those two substances excreted 

 in moderate exercise, were 682.1 grains, and 13.7 grains; and, in 

 hard exercise, as much as 865 grains, and 8.2 grains. The quantity 

 of urea which corresponds with 5.5 oz. of albuminoid food, the active 

 laborer's diet, is 735 grains. The estimates of Haughton are evi- 

 dently low ; if augmented, in accordance with the observations of 



