THE METABOLISM OF THE CARBOHYDRATES 715 



conclusion that may be drawn from the numerous researches of this nature, 

 is that there is no evidence that the blood of a normal animal, even 

 when it is from the pancreatic vein, contains an internal secretion that 

 can restore to a diabetic animal any of its lost power to utilize carbo- 

 hydrates. When the extent of glycosuria alone is used as the criterion 

 of the state of carbohydrate metabolism, serious errors in judgment are 

 liable to be drawn. The condition of the blood sugar and the extent 

 and character of the respiratory exchange are the most reliable indexes. 



DIABETIC ACIDOSIS OR KETOSIS 



Nature and Cause. Much confusion has existed in medical literature 

 over the correct definition of acidosis, mainly because the term was first 

 used for the particular variety of the condition observed in the later 

 stages of diabetes mellitus. The acids which accumulate in the tissue 

 fluids in this disease are acetoacetic and /?-oxybutyric, which are re- 

 lated to acetone and are derived from fatty acids by a faulty metabolism 

 (see page 737). The essential cause of the acidosis is therefore en- 

 tirely different from that in nephritis ; in diabetes foreign acids are 

 added to the blood, whereas in nephritis the acids of a normal metab- 

 olism accumulate because of faulty excretion through the kidneys. 

 The usual signs of acidosis exist in both cases, because the surplus of 

 acid depletes the store of bicarbonate and causes changes in the alveolar 

 00 2 , in the C0 2 -absorbing power of the blood, in the reserve alkalinity, 

 and in the acid excretion by the kidney. It is important to recognize the 

 special nature of diabetic acidosis by a separate name ketosis. 



The chemical processes by which the ketone bodies are produced is 

 discussed elsewhere (page 737). It remains for us to consider the 

 general nature of the metabolic disturbance responsible for their ap- 

 pearance in diabetes. 



For the thorough combustion of fat in the animal body a certain 

 amount of carbohydrate must be simultaneously burned. Fat evidently 

 is a less readily oxidized foodstuff than sugar; it needs the fire of the 

 burning sugar to consume it. If the carbohydrate fires do not burn 

 briskly enough, the fat is incompletely consumed; it smokes, as it were, 

 and the smoke is represented in metabolism by the ketones and derived 

 acids. Such a closing down of the carbohydrate furnaces may be 

 brought about either by curtailment of the intake of carbohydrates, as 

 in starvation (page 600), or by some fault in the mechanism of the 

 furnace itself, as in diabetes. Besides fat, protein may also contribute 

 to the production of ketones when carbohydrate combustion is de- 

 pressed. Fundamentally, therefore ketosis in diabetes is due to the 



