546 METABOLISM, NUTRITION AND DIETETICS 



which a strictly antidiabetic diet is desired. It is much more im- 

 portant to exclude carbo-hydrates largely or entirely from the food, 

 although oatmeal and potatoes are said to occupy an exceptional 

 position, and have even been recommended as beneficial. Calcium 

 chloride has been stated to diminish the sugar excretion in diabetes 

 (Boigey), and it has a similar effect in certain of the artificial glyco- 

 surias (Brown, Fischer). 



In many cases, even when carbo-hydrates are completely, or 

 almost completely, omitted from the food, sugar, derived from the 

 breaking-down of proteins, and possibly to some extent from fats, still 

 continues to be excreted, although in smaller quantity. Other prod- 

 ucts formed or imperfectly transformed in the deranged metabolism, 

 especially of fats, such as acetone, aceto-acetic acid, and oxybutyric 

 acid (the so-called acetone bodies) , may also appear in the urine, or, 

 accumulating in the blood, may, by uniting with its alkalies, seriously 

 diminish the quantity of carbon dioxide which that liquid is capable 

 of carrying, and thus lead to the condition known as diabetic coma. 

 The small amount of carbon dioxide in the venous blood may also be 

 partly due to the hyperpnoea, marked by increased depth of the 

 respiratory movements produced by stimulation of the respiratory 

 centre by other substances than carbon dioxide. The increased 

 ventilation causes a fall in the carbon dioxide pressure in the alveolar 

 air, and therefore an increased elimination of that gas from the blood. 

 This form of coma appears to be really in part an acid-poisoning 

 comparable to the condition produced in animals by doses of mineral 

 acids too large to be neutralized by the ammonia split off from the 

 proteins. The administration of very large doses of alkalies (sodium 

 bicarbonate, for instance, to the amount even of hundreds of 

 grammes) has been recommended for the treatment of this serious 

 complication, and in many cases it is successful in staving it off for 

 a time. Often, however, in spite of a prolonged course of treatment, 

 during which the urine has continued distinctly alkaline, fatal coma 

 eventually occurs. The coma then is not merely a symptom of 

 acidosis, but is also due to the specific toxic effects of the acids even 

 when neutralized. Other toxic products may also be formed in the 

 deranged metabolism. The appearance of the acetone bodies in 

 diabetes presents a problem which cannot be said to have been as yet 

 completely solved. Oxybutyric acid, from which aceto-acetic acid 

 and acetone are easily derived (p. 558), seems to be one of the inter- 

 mediate steps in the normal metabolism of fats. But whereas under 

 ordinary circumstances it is readily oxidized in the body, in diabetes 

 the power of the tissues to burn oxybutyric acid seems to suffer just 

 as does the power to utilize dextrose. The suggestion that in diabel es 

 the abnormally great consumption of fat entailed by the loss of avail- 

 ability on the part of the carbo-hydrates causes the intermediary 

 metabolism of fats to be scamped, as it were, is not satisfactory. 



