1881.] Physiology of Sugar in the Animal System. 



427 



into sugar. If the necessity existed for having recourse to such a 

 prolonged operation as boiling for four hours, a serious obstacle would 

 be offered to the performance of the quantitative determination to 

 which we have to look for the supply of information. To shorten the 

 time of exposure, I at first employed a stout glass flask with a vul- 

 canised rubber bung wired into its mouth, and immersed this in an 

 oil-bath heated to a considerably higher temperature than that of 

 boiling water. Finding that I could not make sufficiently rapid 

 progress with my investigations by proceeding in this way, I had a 

 stout copper boiler constructed for the application of heat under 

 pressure. It is provided with a lid which is screwed down with iron 

 bolts, and has a lever safety-valve with a shifting weight to regulate 

 the pressure. The boiler is large enough to receive a number of flasks, 

 so that several products can be operated on at a time. I am in the 

 habit of working it at 45 lbs. pressure, which gives a temperature 

 just under 300° F. At this temperature, the conversion into glucose is 

 accomplished within about a quarter of an hour. It is reliably secured 

 by exposure for half an hour, and this time I am in the habit of 

 allowing. 



The quantity of sulphuric acid used is in the proportion of about 

 4 per cent, of the strong acid to the volume of liquid that is being 

 worked upon. It is essential to give attention that the conditions are 

 not such that the acid is appropriated to the liberation of another acid 

 unendowed with the power of exerting a converting influence : such, 

 for instance, as would occur if acetic acid had been previously used so 

 as to leave a considerable quantity of acetates present. 



From the amount of glucose, which, through the ammoniated 

 cupric test has been ascertained to be produced, the quantity of 

 Bernardin (glycogen) is calculated. The accepted formula for 

 Bernardin is the same as for starch, viz., C 6 H 10 O 5 . The formula for 

 glucose is C 6 H 12 6 . The equivalent of the one is 162 and of the 

 other 180. From these we obtain the factor for the conversion of 

 glucose figures into Bernardin figures : — 



Let x = the amount of Bernardin equivalent to one part of glucose. 



Then, as 180 : 162 :: 1 : x, 



or x— — — ='9. 



180 10 



Hence *9 stands as the factor to multiply by to convert glucose figures 

 into Bernardin figures. 



I have shown that after the extraction of glucose from blood by 

 alcohol, there is to be found a material which gives no cupric oxide 

 reducing action before treatment with sulphuric acid and heat but 

 does so afterwards. Water dissolves out a certain portion of this 



VOL. xxxii. 2 G 



