86 Dr. jMitchell on (he Occurrence of Sugar in the Animal Economy. 



the first five hours the quantity of sugar increased rather than otherwise, 

 but after that tuuc it gradually went on diminishing until the quantity . 

 became too small for detection. It thus appeared that when starch was 

 injected into the circulation, the blood at once possessed the power of 

 converting it into sugar, and thereafter, by some similar influence, of 

 causing it to disappear. 



But as the artificial introduction of starch into the veins is not one of 

 the regular phenomena of life, it became interesting to ascertain if the 

 blood of an animal, nourished on substances containing a large proportion 

 of starch, would indicate the presence of sugar. A dog was therefore fed 

 on a mixture of boiled potatoes and lard for several days, and then, while 

 in full digestion, a vein was opened and sugar readily detected in the 

 blood. The same experiment frequently repeated always gave the same 

 result, and this uniformity naturally led to the following conclusion : — 

 that the existence of sugar in the blood is not, as formerly supposed, a 

 state of disease, but the normal or regular consequence of the digestion 

 of aliments containing starch or sugar itself. 



This deduction was the more readily drawn from the notion, which 

 was so generally admitted, that animals have not the power of creating 

 any immediate principle, such as albumen, fibrin, casein, &c. ; but only 

 possess the power of apj^ropriating and then destroying such of these as 

 are furnished ready made by the animal or vegetable kingdoms. I say 

 the power of creating sugar, or forming it de novo, being thus 

 denied to the animal organism, to maintain consistency it became directly 

 necessary to attribute its presence in blood to the use of feculent or 

 saccharine food. 



The matter, therefore, stood thus, — Men had observed that during the 

 digestion of a food containing sugar or starch, the blood of animals con- 

 tained sugar, and they therefore concluded that it had been furnished by 

 these aliments. 



Comparative experiments shall show in how far this was correct. 

 But before proceeding to their enumeration, I cannot refrain from 

 alluding to the postscript of a paper " on the "White or Opaque Serum of 

 the Blood," read to this society by Dr. Andrew Buchanan. He states 

 therein, that his experiments on that subject led him to suspect that the 

 starch might be converted by the organs of digestion into sugar, and be 

 absorbed in that form into the blood. Accordingly, he treated with 

 yeast some serum of blood, which had been withdrawn about three hours 

 after a full meal, and found that fermentation ensued. The same experi- 

 ment was repeated, and the result again was affirmative of the presence 

 of sugar. 



lu the second case, however, there was one difference worthy of note, 

 — while the feculent diet had been used more sparingly, the sugar appeared 

 to exist more abundantly. And what seemed still more strange was, that 

 the serum of the blood of the same individual after fastimj still indicated 

 the existence of sugar, though in small (juantity. 



