Dr. Mitchell oii the Occurrence of Sugar in the Animal Economy. 95 



and particularly in carnivorous animals, when appropriately fed, this 

 function is little called into action, and its existence therefore is probably 

 intended merely as a resource to fall back upon in case of necessity. 

 Without it, however, animal life would be most precarious, or, in many 

 instances, even impossible." 



With these remarks I shall conclude the first part of my subject, and 

 proceed at once to the examination of the great and important question 

 which at once presents itself as now requiring an answer : — How, or by 

 what agency, and in what part of the system, does this sugar disappear 

 from the blood ? 



I have hitherto dealt with my subject in a pui'e chemico-physiological 

 light, nor do I pm-pose doing differently in that part of the paper which 

 is to follow- I may state, however, that these researches have been 

 undertaken by me, and possess an interest to my mind, in as far as they 

 may possibly lead to some rational, and I hope successful, method of 

 treating that most distressing disease, wherein sugar appears in the urine, 

 and which has hitherto been regarded as beyond the reach of the vis 

 medicatrix. 



SECOND PART. 



How is this sugar which has been shown to exist in the blood and 

 liver caused to disappear ? How is it destroyed '? By what agency, and 

 under what influences ? What are the products of its transformations, 

 and in what part of the system do they take place ? 



Such is the problem, in the attempt to solve which I have been for 

 some time occupied. I proceed at present to lay before you a few facts 

 bearing on this interesting subject. 



The changes which sugar undei-goes when bi'ought into contact with 

 other bodies, having a marked influence on it, are not confined to any 

 narrow limits, like those of inorganic bodies, but are, in fact, unlimited. 



In inorganic compounds, we find that acid acts upon a particular con- 

 stituent of the body, which it decomposes by virtue of its aflinity for that 

 constituent, and its proper chemical character is maintained in whatever 

 form it be applied. "But when the same body acts upon sugar, producing 

 great changes in that compound, it does this, not by any superior affinity 

 for a base existing in the sugar, but by disturbing the equilibrium in the 

 mutual attraction of the elements of the sugar amongst themselves. 

 Muriatic acid and sulphuric acid, which differ so much from one another 

 both in properties and composition, act in the same manner upon sugar, 

 but the action of both varies according to the state in which they are ; 

 thus, they act in one way when dilute, in another when concentrated, and 

 even difference of temperature causes a change in their action. Thus, 

 sulphuric acid of a moderate degree of concentration converts sugar into 

 a black carbonaceous matter, forming, at the same time, acetic and formic 

 acids. But when the acid is more diluted, the sugar is converted into 

 two brown substances, both of them containing carbon, and the elements 



