IS 13.] discharged in Diabetes Mellitus. 3S 



tation on adding nitric acid to the dissolved extract. This is a 

 state of the urine, also, which is often produced by the exclu>Ive 

 use of animal diet. In such cases, I have endeavoured to deter- 

 mine the proportions of the urea and saccharine matter to each 

 other, by the following process ; A portion of the extract was 

 first decomposed by destructive distillation ; and the product 

 then redistilled with the addition of carbonate of potash. The 

 condensed liquid was next saturated by diluted sulphuric acid of 

 known specific gravity ; and from the quantity of this acid which 

 was required, 1 inferred, that of the solid ammoniacal carbonate, 

 every two parts of which were assumed to indicate three of urea. 

 This process I believe to be much more accurate than the treat- 

 ment of such a mixed extract with nitric acid ; because nitrate 

 of ammonia will be formed, and will be mixed with the crystals 

 of oxalic acid, thus rendering their apparent, greater than their 

 real quantity. The precision, however, which is attainable in 

 this way, can only be required in experiments of research. For 

 all practical purposes, the use of the hydrometer, and the appli- 

 cation of the test of nitric acid to the extract, will afford a 

 sufficient measure of the degree in which the urine deviates from 

 the healthy standard. 



Two hypotheses have been framed to account for the principal 

 phenomena of diabetes. According to the one, the seat of the 

 disease is solely in the organs of assimilation. But it has been 

 satisfactorily proved that saccharine matter does not exist ready 

 formed in the serum of diabetic blood.* Until, therefore, it 

 can be shown that there is a direct communication between the 

 digestive organs and the kidneys or bladder, capable of conveying 

 ^ugar from the former to the latter without its passing through 

 the general circulation, the theory must be modified by assuming 

 that the blood which reaches the kidneys contains the elements oi 

 sugar, and is deficient in those of urea. To this theory, how- 

 ever, which takes for granted the healthy state of the kidneys, it 

 may be urged as an objection, that it supposes those glands to 

 have a natural tendency to secrete sugar whenever its elements 

 are presented to them. But this is a point which can scarcely 

 be conceded ; for besides that the secretion of urea is known to 

 go on under the exclusive use of vegetable food, such a function 

 in the kidneys would be inconsistent with that wise adaptation of 

 parts, which devotes every organ to some specific purpose essen- 

 tial to the healthy state of the animal economy. It appears, 

 therefore, to be necessary to a just pathology of the disease, that 

 some morbid condition of the kidneys should be admitted, though 



* Nicholas and Gueudeville, Ann de Ch. xliv, 69; Dr. Woilaston, Phil. 

 Mag, xxxvii. 79; and my own experiments, the result of which is stated in 

 Dr. Ferriar's Medical Histoi'ies, 2d edit. i. 146. The same couciusioa is esta- 

 blished, also, by experiments which I have very lately made. 



Vol, I. N^I, C 



