142 FAMILY STUDIES IN BUILD. 



the same for each steer. The digestibility of the total ration was 

 determined at intervals; four tests were made of each animal in the 

 respiration calorimeter to determine the percentage availability of 

 the energy of the feeds consumed by each. The results were as fol- 

 lows: Analysis of feces and urine failed to show any difference in per- 

 centage digestibility of the food by the two animals, and calorimeter 

 tests failed to show any difference in the proportion of the food- 

 energy which was being metabolized. But the two animals did not 

 metabolize in the same way. Thus, in the scrub, a larger proportion of 

 the gain made was of protein than in the case of the beef steer ; and, 

 conversely, the gain of the beef steer was more largely fat than in the 

 case of the scrub. Reduced to common weight, the energy require- 

 ment for maintenance of the scrub steer was nearly 19 per cent 

 greater than for the beef steer. Since the beef steer would eat more 

 than the scrub and tended to store fat rather than protein, the greater 

 tendency of the beef steer to fatten received a biochemical explana- 

 tion. The results seem to show a difference between the two varieties 

 in the working over of the assimilated materials. 



Indeed, it is easily appreciated that steers of the beef and dairy 

 types of cattle should metabolize differently when we consider the 

 marked difference in the milk production of the cows of these two 

 types. The cow of the highest dairy type is capable of manufacturing 

 20 kilograms of milk containing 1.2 kilograms of butter fat in one 

 day, or 6 per cent (Bailey, Encl. Am. Agric, III, 365). The cow of the 

 meat type, of larger size, produces up to 30 kilograms of milk, and 

 this contains, perhaps, 1.3 kilograms of butter fat per day, or only 4.3 

 per cent (Sinclair, 1904, p. 740-42). There is here, obviously, a differ- 

 ence in the metabolic processes in the cows and this is reflected in 

 the steers also.* There is an internal biochemical difference as well 

 as a difference in the feeding instinct. The latter is not merely a 

 matter of family tradition, of the family economics or mores; it is 

 a physiological phenomenon as much as internal metabolism. 



Indeed, even von Noorden (1907, III, p. 700) seems to be forced 

 to this conclusion by cases of failure to reduce weight at a diet far 

 below that which appears to be essential to maintenance. Thus a 

 man of 39 years, who exercised freely in the open air, had a weight of 

 102 kg. For 3 months his diet never exceeded 1,720 calories (esti- 

 mated at 1,000 calories short of normal requirements) and at the end 

 of this period he weighed 101 kg. 



That a relation between ingested food and activity is not the 

 entire explanation of obesity is recognized by medical men of experi- 

 ence. Heckel (1920, p. 371), referring to recurrent obesity, remarks 

 on its frequency and says: To constitute an obesity there must be 



• I am indebted to Mrs. C. D. Walcott for calling my attention to this point. 



