67 



ration consisted of hay; in the third series, of oats and straw; in the 

 fourth series, of hay and straw; in thetifth series, of maize and straw; 

 in the sixth series, of horse beans and oat straw, and in the seventh 

 series, of maize cake and oat straw. Analyses were made of the food^ 

 urine, and feces. 



The effect of the rations and their digestibility was studied while the 

 horses were at rest, walking, trotting, at work while walking, and at 

 work while trotting. The work consisted in turning the arm of a 

 dynamometer a definite number of times. Experiments were also 

 made in which the horses drew a vehicle. The effects of the rations 

 under different conditions of rest and work on temperature and weight 

 of the animals were studied. Many of Grandeau's and Leclerc's 

 deductions have already been referred to, one of the most interesting 

 being a demonstration of the high value of maize as a food for horses. 



MEASURING THE RESPIRATORY QUOTIENT AND THE DEDUCTIONS 



DRAWN FROM IT. 



Experiments in which the respirator}^ quotient was determined are' 

 perhaps less numerous than those mentioned above. A determination 

 of the respiratory quotient necessitates the measurement and analysis 

 of the air taken into the lungs and excreted from them. The experi- 

 ments which have been made in Germany are ordinarily carried on 

 with the aid of a mask which covers the head, or by the insertion of a 

 silver tube in the trachea. In both cases the air is breathed in and 

 out through tubes provided with suitable valves, so that the air enters 

 through one tube and leaves through the other. The air is measured 

 and the samples analyzed. The ratio of oxygen consumed to carbon 

 dioxid expired in a unit of time is called the respiratory quotient. 



Zuntz" and Hagemann and their associates have carried on a very 

 extended series of investigations with horses. In most of these cases 

 the respiratory quotient was determined. In many other cases other 

 determinations, including the balance of income and outgo of nitrogen 

 and carbon, were also made. Work was performed with a sort of 

 treadmill and the amount could be measured. The deductions drawn 

 from these experiments are of great interest, and some of the principal 

 ones follow. 



A horse weighing from -iOO to 500 kilograms (880 to 1,100 pounds) 

 excretes 26 to 40 liters (27 to 42 quarts) per minute from the lungs 

 when no work is performed. If a horse takes exercise by walking 

 the amount is increased to 80 to 90 liters (84 to 95 quarts) per minute. 

 If 75 kilograms (542 foot-pounds) of work is done per second the 

 respired air increases to 300 liters (317 quarts) per minute. If the 



aLandw. Jahrb., 27 (1898), Sup. Ill; see also Deut. Landw. Presse, 23 (1896), 

 pp. 561, 571, 579. 



