E. T. Halnan 171 



From Kiihii and Kelhier's results, and the experiments of Arinsby, 

 it is evident that the estimate given by Wolff and the older authorities, 

 and included by Kellner in his appendix for the maintenance of a 

 1000 lb. ox at rest, is much too high, and that the energy requirements 

 of an ox of this weight are satisfied on a diet supplying -0 lb. digestible 

 protein and 10,840 cals. per day, i.e. a maintenance starch equivalent 

 of 6-35 lbs. per day. In other words the " generally accepted rati(.)n " 

 of 20 lbs. hay per day for a 1000 lb. ox is much too generous for main- 

 tenance purposes and should be replaced by a ration of 14 lbs. hay per 

 day. Murray's criticism of the value to be attached to the conclusions 

 reached by Wood and Yule in their paper consequently becomes point- 

 less. The following table summarises the estimates of various authors 

 of the maintenance rec^uirements of an ox at rest, the results being 

 calculated in every case to the needs of a 1000 lb. ox. 



Maintenance Requirements of Oxen. 



Maintenance In calories 



Author starch equivalent per 1000 lbs. L.w. 



Henneberg and Stohmann .... 8-1 13,830 



Wolff (Appendix) 9-2 15,700 



Kellner (Appendix) U-0 10,380 



Kiihn 7-5 12,850 



Kelhier (1896) 7-1 12,200 



Arm.sby (1898) 7-0 11,980 



Kelhicr ( 1900) 6-35 10,840 



With regard to the graph, the data derived from Die Erndhrung 

 on which the graph is based certainly depend upon the application of 

 Rubner's^ surface law, and the data given were calculated by Kellner- 

 on this basis. But the figure from which they were calculated is an 

 average of experiments of long duration on seven oxen, and this 

 estimate of the energy requirements of an ox, namely 13,470 cals. for 

 maintenance of a 632 kg. ox, at 15-5° C. or 10,840 per 1000 lbs. live weight, 

 is an experimental determination. The truth of Rubner's surface 

 law, derived from experiments on dogs (presumably adult) varying 

 from 3-2 to 31 Idlos., is freely accepted by Murray. While in no way 

 criticising the accuracy of Rubner's results, or the universal applicability 

 of this law, the possibility of a modification of our ideas on this subject 

 in the light of future research must clearly be borne in mind. Rubner's 

 law states that the energy metabolism is proportional to the superficial 

 area of the animal. In other words, the metabohsm varies as the 

 amount of heat loss at the surface, and its variation in accordance 



1 Rubner, Zeitschrift fiir Biologic, 1883, 19, 535. 

 ^ Kelhier, Die. Erndhrung Land. Nutziiere, p. 395. 



