520 PRINCIPLES OF ANIMAL NUTRITION. 
muscles in a particular way seems to increase their average mechan- 
ical efficiency. 
Gruber,* in two series of experiments upon himself, obtained 
the following figures for the excretion of carbon dioxide during 
rest, horizontal locomotion, and hill climbing, all the trials being 
made about the same length of time (four to five hours) after the 
last meal: 
Work of Carbon Dioxide 
Ascent, Excreted in 20 
Kgm. Minutes, Grms. 
Series I; 
TOS cosh fiaauauaritia Gacasaauctasimnea og mo gaon pau dsate| tale wed eee ene 9.706* 
Horizontal locomotion... ...........0 00 cleccceeeceeeees 19.390* 
Hill climbing without practice Misia loalererelas 5892 40.982 
«« ~ after 12 days’ practice..... 6076 32.217 
Series IT (2 months later): 
PROS toca. Goes scars aa ouar lends see maven aaaain we cumoa Saas wane aelatee 12.833 
Horizontal locomotion...............00.[sccceeeeeeeeee 22.418 
Hill climbing without practice.......... 7376 38 .832T 
«after 14 days’ practice... .. 7539 31.001 
* Some carbon dioxide may have escaped absorption. 
t Some carbon dioxide lost. 
Schnyder ¢ has confirmed and extended Gruber’s results. In 
experiments in a treadmill upon two different subjects he ob- 
tained the following figures for the work performed per gram of 
carbon dioxide excreted in excess of that given off during rest: 
; Kem. 
Nod ; Without training...................0000000, 218.13 
Sener Sty ae wae After 2 months’ training.................... 253.18 
Without training..................0.0.0 000008, 243 .93 
INO? Qu iccnweee sate 1 After 6 days’ training...................... 285 . 52 
6-551 EY ats dearer ay ace ie St 349.40 
' Without training....................0000005 302.76 
No. 2 (second series) After 47 days’ training..................... 404.39 
That the greater efficiency after training is not due solely to a 
diminished use of accessory muscles is shown by Schnyder’s experi- 
ments on convalescents. His results were as follows: 
* Zeit. f. Biol., 28, 466 
+ Ibid., 88, 289. 
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