ANALYSIS OF DIABETIC URINE. 035 



but a very small quantity of sugar, we still deemed it nc^ 



cessary, to compare it with this substance in all its proper- 



tie*, in order to place the fact in the strongest light, and 



thus discover all the characters proper to the peculiar prjii- 



ciple, of which it appears to be almost wholly formed^ For 



this reason we examined the action of alcohol on it, which 



does not attack the saccharine principle, and that of nitric 



acid, which does not convert any portion of this principle 



into mucous acid. The first of. these reagents, at the terii- iiotalcolioi 



perature of C0° [140° F.l dissolved so large a quantity of ^^uk up so 



^, , ■- T -4. i- J f ^ 1 • niuchasiobe- 



manna, that on cooling it rormed a mass ot crystals in come solid on 

 groups, the crystals in each group issuing from a conimou cooimg. 

 centre. The second prpduced in it by long continued boil- Nitric acid con- 

 ing such a large deposit of mucous acid, that the weight '^erted h;ilt to 

 ' 1 1 1 If 1 ',> 1 1 mucous acii, 



was nearly equal to hall that ot the manna employed. 



Here then we have two more characters, that strikingly Thespcharac- 

 distinguish sugar properly so caljed from the peculiar p;ii.- tiisdistin-iush 



' . , p ■ . . . ' manna from 



ciple 01 mannji. sn.ar 



No doubt farther research would exhibit many otlK^rs and perhaps 

 TOore or less striking ; but as those we have related are suf- others. 

 ficient, to make those two substances be considered as per- 

 fectly distinct from each other, we did not think it neces- 

 sary to push our examination farther. 



Hence it follows, that it will always be an easy matter to This prindp^e 

 discover and to separate manna, or rather the peculiar prhi- parable by aU 

 ciple of manna, whatever be the substances with which it i.s cohol. 

 mingled. All that is necessary is to treat the matter con- 

 taining it with hot alcohol, and it will be almost entirely 

 precipitated by cooling. Indeed there are other vegetable 

 substances, that possess this property even in a sti Iking de- 

 gree; but as these substances are found only in this class of 

 acids, it is always practicable to deprive it of these, by com- 

 bining it with an alkaline or earthy saliliable base, or a me- 

 tallic oxide, according to the nature of the acid ; and con- 

 sequently this mode of separation may be generally em- 

 ployed. 



Thus we may ascertain, whether the honeydew observed Honeydevf? 

 on the leaves of certain trees, particularly those of the lime, 

 1)6 really a species of manna; and if it be the same with and saccharine 

 the sacchuviue principle that exists iu asparagus, and which principle in as- 



