522 A MANUAL OF PHYSIOLOGY 



After the preliminary sweeping out of the sugar already in 

 the body a definite ratio is established between the dextrose 

 and the nitrogen eliminated in the urine (dextrose : nitrogen 

 : : 3' 6 or 37 : i). The sugar at this stage is produced entirely 

 from proteins, and not at all from fat. The degree of intoler- 

 ance for carbo-hydrates in pathological diabetes may be arrived 

 at by putting the patient on a diet of protein and fat (rich 

 cream, meat, butter, and eggs), and determining the ratio of 

 dextrose to nitrogen excreted. If it is 3*6 to 37 : i, intolerance 

 is complete, none of the dextrose produced from protein being 

 burrjed, and there will probably be a quickly fatal issue (Lusk 

 and Mandel). There is some evidence that, in addition to the 

 increased permeability of the kidney to sugar and the diminished 

 power of the tissues in general to destroy it, the renal epithelium 

 is actually an important seat of the sugar production (Brodie). 



In adrenalin glycosuria the sugar-content of the blood is 

 increased. Subcutaneous injection of adrenalin chloride causes 

 a mild, intravenous injection a greater glycosuria, and intra- 

 peritoneal injection the greatest glycosuria of all (Herter). The 

 best evidence is that the glycosuria is produced by some action 

 on the liver, possibly through the excitation of sympathetic fibres 

 controlling the production of dextrose from glycogen (Underhill 

 and Closson), or by a direct effect on the hepatic cells, which 

 hastens the normal transformation of glycogen into dextrose, or 

 hinders the normal transformation of dextrose into glycogen. 

 After repeated injections of adrenalin a tolerance for it is 

 established, and glycosuria is no longer caused. 



3. Metabolism of Fat. The fat, passing along the thoracic 

 duct into the blood-stream, is very sopn removed from the 

 circulation, for normal blood contains only traces, except during 

 digestion. Where does it go ? What is its fate ? 



The presence of adipose tissue in the body might suggest a 

 ready answer to these questions. The fat-cells of adipose tissue 

 are ordinary fixed connective-tissue cells which have become 

 filled with fat, the protoplasm being reduced to a narrow ring, 

 in which the nucleus is set like a stone. It would, at first 

 thought, seem natural to suppose that the fat of the food is 

 rapidly separated by these cells from the blood, and slowly given 

 up again as the needs of the organism require, just as carbo- 

 hydrate is stored in the liver for gradual use. And it has been 

 found that a lean dog, fed with a diet containing much fat and 

 little protein, puts on more fat, as estimated by direct analysis, 

 or keeps back more carbon, as estimated by measurements of 

 the respiratory exchange, than can be accounted for on the 

 supposition that even the whole of the carbon of the broken- 

 down protein corresponding to the excreted nitrogen has been 



