LIPID STORAGE UNDER ABNORMAL CONDITIONS 631 



of energy output, as well as to the level of food intake. According to In- 

 gle, 539 it represents a principle long recognized in medicine and in animal 

 husbandry. When adult male rats were confined in cages 9 inches long, 

 4.5 inches wide, and 4.5 inches deep, and were given an appetizing fluid diet 

 ad libitum, the maximum body weights attained all exceeded 700 g. ; one 

 rat reached a maximum body weight of 1090 g. In contradistinction to 

 these levels, Ingle 539 states that he has never recorded a weight greater than 

 550 g. for adult male rats on the stock diet, nor one greater than 600 g. 

 when they were fed on a fluid diet. 



d. Hereditary Obesity in Mice. Certain strains of mice are known to be 

 especially susceptible to obesity. Thus, Fenton and Carr 540 and Fenton 

 and Dowling 541 noted that, although it is the rule for mice of many inbred 

 strains to become obese late in life without special nutritional manipula- 

 tions, this rarely occurred in the case of younger animals. However, when 

 mice were placed on diets of increasing fat content, an increased weight 

 (which was interpreted as synonymous with a higher fat deposition) could 

 be produced in rats of the C 3 H and A strains, but not in the case of animals 

 from the C57 and I strains. 540 Whereas the average fat content of mice of 

 the A strainatthree months on two representative diets was 24.6 and 25.2%, 

 the mean value for mice of the I strain on these diets was only 13.1 and 

 8.7% at this age. 541 In a later study from the same laboratory, 542 it was 

 shown that mice of the C57 and C 3 H strains both consumed considerably 

 more calories when fed a 50% fat diet than when given the 5% fat regimen. 

 Moreover, the oxygen consumption was higher in mice of the C 57 strain on a 

 50% fat intake than on a diet containing 5% of fat, indicating that the in- 

 creased calories consumed on the high-fat diet were at least partly oxidized. 

 On the other hand, no greater oxygen consumption occurred in the case of 

 the C 3 H strain on the high-fat diet than in those on the low-fat diet, in spite 

 of the fact that the intake of calories was greater in the former case. Thus, 

 the extra calories consumed were deposited as carcass fat. This differ- 

 ence in ability to oxidize extra fat exhibited by these two strains of mice 

 may well explain the predisposition of the C 3 H strain to develop obesity. 



According to Mayer et al., 5i3 the obese-hyperglycemic syndrome in mice 

 is a Mendelian recessive condition, characterized by adult weights in the 60 

 to 115 g. range, atrophy and ulceration of the skin, hyperglycemia, and 

 glycosuria. The obese animals were shown to exhibit atypical distribution 



540 P. F. Fenton and C. J. Carr, /. Nutrition, 45, 225-233 (1951). 



541 P. F. Fenton and M. T. Dowling, /. Nutrition, 49, 319-331 (1953). 



642 J. B. Lyon, Jr., M. T. Dowling, and P. F. Fenton, J. Nutrition, 51, 65-70 (1953). 

 543 J. Mayer, D. N. Silides, and M. W. Bates, Federation Proc, 12, 423 (1953). 



