Decembee 10, 1915] 



SCIENCE 



819 



abundant food the cells produce heat in 

 increasing measure. Thus, after giving 

 meat alone in large quantity to a quietly 

 resting dog the heat production may be 

 double that of the normal basal metabol- 

 ism. The constituent amino-acids of pro- 

 tein are relieved of their NHa groups and 

 the denitrogenized remainders are utilized 

 for heat production, any excess being eon- 

 verted into glucose and retained in the or- 

 ganism a^ glycogen. The great rise in heat 

 production is in large measure due to the 

 direct chemical stimulation of the cells 

 through the metabolism products of cer- 

 tain amino-acids. The proof of this lies 

 in the fact that if glycocoll or alanine be 

 given to the diabetic dog the heat produc- 

 tion is largely increased, although these 

 substances are not oxidized and there is 

 therefore no evolution of heat from them, 

 for they are converted into glucose and 

 urea which appear in the urine. "When the 

 same method is applied to the study of the 

 sugars, it fails to support the idea that the 

 intermediary products of sugar metabolism 

 directly stimulate the cells to a higher heat 

 production. Thus, fructose administered 

 to a diabetic dog caused no increase in 

 heat; production, although it underwent 

 chemical change, for it was found as glu- 

 cose in the urine. Since all the evidence 

 regarding this reaction points to a prelimi- 

 nary cleavage of fructose which contains 

 six carbon atoms into two molecules each 

 containing three atoms of carbon and to 

 the subsequent synthesis of these mole- 

 cules into glucose, one may reason that the 

 preliminary cleavage products of carbohy- 

 drate metabolism are not direct stimuli to 

 protoplasm, as are those of amino-acids like 

 glycocoll and alanine, but that normally 

 the mere presence of a large number of 

 metabolites of sugar results in their oxida- 

 tion in increased measure. 



Rubner has shown that when the yeast 



cell is bathed in a solution of sugar and 

 peptone the protein is used for growth or 

 cell repair only, while alcoholic fermenta- 

 tion furnishes the energy, and as before 

 stated the quantity of this energy is inde- 

 pendent of the strength of the solution. So 

 also in a mammal such as the dog, if one 

 give 50, 70 or 100 grams of glucose, the 

 energy production increases in all cases to 

 a level of about 30 per cent, above the nor- 

 mal. It appears that the cells by a process 

 called "self -regulation" use the fragments 

 of broken glucose up to a certain limit 

 which is not transcended. Any excess of 

 these fragments is converted into glycogen 

 or into fat, a small quantity of energy 

 being absorbed in the first process and a 

 small quantity being liberated in the sec- 

 ond. The result of this is that beyond a 

 certain limit of carbohydrate plethora, the 

 heat production in the dog scarcely rises, 

 and this is analogous to the behavior of the 

 yeast cell towards its nutritive environ- 

 ment. 



The study of the intermediary metabol- 

 ism upon which the total heat production 

 of an animal is based, furnishes a fascina- 

 ting field for the scientist, and it is also 

 evident that the study of the fuel require- 

 ment of the human individual in health and 

 in disease presents many problems of im- 

 portance for the general welfare of the 

 community at large. 



Gkaham Lusk 



OBSTACLES TO BESEASCm 

 The duty of the university to investigate 

 the unknown as well as to teach the known is 

 clearly evident. In the performance of this 

 duty, the importance of research work is em- 

 phasized in many ways. Promise of produc- 

 tive scholarship is a leading qualification de- 

 manded in selecting members of the faculty. 

 Encouragement and facilities for original 



1 An address delivered before the Minnesota 

 Chapter of the Sigma Xi Society, October 21, 1915. 



