TEMPERATURE OP THE WATER USED IN INFUSION. 143 
water, does not proceed so rapidly as in the one made with 
cold water, and if the infusion be examined from time to 
time during the progress of the decomposition, the large 
quantity of starch which it originally contained, will be 
found to be gradually disappearing, and ultimately a solu- 
tion of iodine will not detect its presence — it will have total- 
ly disappeared. 
Now the two substances which appear to be principally 
concerned in these changes, are, vegetable albumen and 
starch; and these bodies are known to be present in con- 
siderable quantity in calumba root. 
Albumen, when in solution, is especially characterized 
by great instability, mere contact with atmospheric air being 
sufficient to induce rapid decomposition. Starch, on the 
other hand, is a much more stable body, and the changes 
which it undergoes are generally induced by the presence 
of some albuminous matter acting as a ferment. 
When the infusion is made with cold water, the albumen 
is dissolved out from the root unaltered, and the presence 
of this body soon gives rise to decompositions which render 
the infusion unfit for use. 
If the infusion be made with boiling water, the albumen 
will be partially coagulated, rendered less soluble, and not 
so liable to undergo decomposition. Nevertheless, it is 
probable that a portion of albuminous matter taken up, 
even in this case, by the water, is the cause of the subse- 
quent change which is found to take place in the starch. 
Thus I find that if an infusion, whe her made with cold or 
with boiling water, be subsequently heated to the boiling 
point, it will keep for a much longer time, without under- 
going decomposition, than it otherwise would ; and this 
seems to indicate the necessity of scalding out the infusion 
jug before making this infusion, so that the temperature of 
the water should be as near the boiling point as possible. 
There are no doubt some cases in which it may be desira- 
ble to avoid the presence of starch in preparations of this 
kind, and this can only be effected by the use of cold or 
