1881.] Physiology of Sugar in the Animal System. 



425 



was then carefully decanted off and some fresh spirit added and time 

 again given to settle. The next step was to purify the product, and 

 this was done by collecting and dissolving it in a little water, 

 thoroughly acidifying the solution with acetic acid, filtering from the 

 precipitate produced, and then re-precipitating with spirit. The pre- 

 cipitate thus finally obtained was dissolved in water and examined. 

 The solution was found to exert no reducing action upon the aramo- 

 niated cupric test before treatment with sulphuric acid and heat, but 

 did so afterwards. Such is the behaviour of Bernardin (glycogen), 

 and such behaviour, it is to be noted, was obtained from a product 

 furnished by the process of preparation adapted for yielding in a 

 separated form whatever of the principle in question the blood might 

 contain. 



I have spoken of the material I have been referring to, which is 

 precipitable by spirit and convertible into glucose by sulphuric acid 

 and heat, under the name of Bernardin, but I am not prepared to state 

 that the principle which exists in the blood is absolutely identical with 

 that belonging to the liver. The determination of this point must 

 form the subject of future investigation. 



The process I have described is the one by which I learnt that a 

 principle agreeing with Bernardin (glycogen) may be recognised in the 

 blood. A shorter method, however, may be had recourse to for reveal- 

 ing its presence. The blood may be at once treated with potash and 

 the product poured into spirit. The subsequent steps to be followed 

 are those which have been already described. 



It is through the ammoniated cupric test that I have been led on to 

 the acquirement of the information that I have obtained. The delicacy 

 of the test, and the circumstance that its action is not interfered with 

 by the presence of a small quantity of nitrogenous matter, have 

 enabled me to discern conditions which the ordinary application of 

 the cupro-potassic test would have failed to have revealed. Once in 

 possession of the knowledge supplied through the ammoniated cupric 

 test, I could see that the ordinary cupro-potassic test ought to be sus- 

 ceptible of being rendered applicable for revealing the glucose pro- 

 duced from the Bernardin (glycogen) existing in blood, and such, I 

 find, proves to be the case. From half a litre to a litre of blood should 

 be taken and treated by being at once boiled with potash and poured 

 into spirit. The aqueous solution of the ultimate alcoholic precipitate 

 obtained possesses, as will be understood, not the slightest cupric oxide 

 reducing power of its own ; but, after treatment with sulphuric acid 

 and heat, and subsequent neutralisation, gives a good reaction with the 

 cupro-potassic solution used in the ordinary way. The suitability of 

 blood for operating upon to show this result varies, and a specimen 

 should be procured from an animal in good condition and well fed up 

 to the time of death. The blood obtained from the slaughter-house is 



