796 NUTRITION AND HEAT REGULATION. 



alter the nitrogen elimination in the urine. The diabetic condition 

 may be produced in other ways the most interesting of which is by 

 the administration of phloridzin, a vegetable glucosid obtained 

 from the roots of certain trees (apple, pear). The cause of phlo- 

 ridzin diabetes is not entirely known, but the general view is that 

 the glucosid acts upon the kidney and renders it more permeable, 

 so that the sugar of the blood escapes into the urine, or, on the 

 other hand, it may affect the condition of the sugar in the blood so 

 as to make it pass through the kidney more easily. The diabetes 

 in this case has obviously a different cause from that of pancreatic 

 diabetes, but by repeated use of the drug the loss of carbohydrate 

 to the body may be made complete. If the animal is fed only on 

 proteid, proteid and fat, or is starved so that he is living on the 

 proteid and fat of his own body the drug still causes the appear- 

 ance of large quantities of sugar in the urine. Lusk * finds under 

 such conditions that the amount of dextrose in the urine bears a 

 definite ratio to the amount of nitrogen, D : N :: 3.65 : 1. He 

 believes that the establishment of this ratio is an indication of a 

 complete inability of the tissues to use sugar. A similar ratio has 

 been obtained in the urine of individuals suffering from a severe 

 and eventually fatal form of diabetes mellitus. Assuming that 

 the sugar is these cases comes entirely from the proteid of the food 

 or of the tissues, this ratio would indicate that 58.4 per cent, of the 

 proteid molecule may be converted to sugar in the body. 



Nutritive Value of Fats. The fats of food are absorbed into 

 the lacteals chiefly as neutral fats, the so-called chyle fat. They 

 eventually reach the blood in this condition, and are afterward in 

 some way oxidized by the tissues. The final products of their 

 oxidation are the same as when burnt outside the body 

 namely, CO 2 and H 2 O and a corresponding amount of energy must 

 be liberated. Speaking generally, then, the essential nutritive 

 value of the fats is that they furnish energy to the body, and, from 

 a chemical standpoint, they must contain more available energy, 

 weight for weight, than the proteids or the carbohydrates. In a 

 well-nourished animal a large amount of fat is found normally in 

 adipose tissues, particularly in the so-called "panniculusadiposus" 

 beneath the skin, and in the folds of the peritoneum, etc. Physi- 

 ologically, this body fat is to be regarded as a reserve supply of 

 nourishment. When food is eaten and absorbed in excess of the 

 actual metabolic processes of the body, the excess is stored in the 

 adipose tissue as fat, to be drawn upon in case of need as, for 

 instance, during partial or complete starvation. A starving animal, 

 after its small supply of glycogen is exhausted, lives entirely upon 



* See Lusk and coworkers, " American Journal of Physiology, " vols. i 

 iii, and x; also " Deutsches Archiv f. klin. Med.," 81, 472, 1904. 



