PRAXINUS ORNUS. 
209 
length, and two inches wide. The juice, which is thick and white, 
immediately begins to flow, and gradually hardens on the bark ; in 
eight days it acquires the consistence and appearance with which it 
is seen here, when it is collected and packed for sale. Sometimes it 
flows in such abundance from these incisions as to run on the ground, 
by which it becomes mixed with various impurities. Manna is 
distinguished into different kinds ; viz. manna in the tear, canu- 
lated and flaky manna, and common brown manna ; these varieties 
seem rather to depend upon the relative purity of the substance, 
than from any essential diff"erence in it. When the juice transudes 
very slowly the manna is always drier, more transparent and pure, 
and consequently of more value ; but when it flows very copiously, 
it concretes into a coarse, brown unctuous mass. Houel, who tasted 
the manna when flowing from the tree, found it much more bittir^ 
than in its concrete state. 
Medical Properties and Uses. It is supposed that the 
Arabian physicians were the first who used manna medicinally, and 
that by them it was introduced into the other eastern countries. 
It is a mild aperient, and was formerly much used, but it is now 
seldom administered, except in combination with senna, salts, or other 
purgatives, more to cover their taste than to aid their operation ; it is 
a mild and innocent laxative for young children, though it sometimes 
produces griping, and ia this respect, its eff'ects are analogous to 
honey ; from 3i to § ss may be given dissolved in water, or what 
is better, gruel or decoction of pearl barley ; for an adult, from one 
to two ounces will be required, and this alone will sufficiently ac- 
-count for its being discarded as a purgative remedy. 
Oflf. The Concrete Juice, called Manna. 
