FRAXINUS ORNUS. ORD. XXXV. Ascyroidec. 593 
to depend upon their respective purity, and the circumstances in 
which they are obtained from the plant, than upon any essential 
difference of the drug: when the juice transudes from the tree 
very slowly, the Manna is always more dry, transparent, and pure, 
and consequently of more estimation; but when it flows very 
copiously it concretes into a coarse brown unctuous mass; hence 
we have a reason, why, by applying straws and other substances 
to receive the flowing juice, the Manna becomes much improved : 
Houel, who tasted the manna when flowing from the tree, found 
it much bitterer than in its concrete state; this bitterness he 
attributes to the aqueous part, which is then very abundant, of 
course the manna is meliorated by all the circumstances which 
promote evaporation. According to Lewis, “ the best Manna is 
in oblong pieces, or flakes, moderately dry, friable, very light, of 
a whitish or pale yellow colour, and in some degree transparent : 
the inferior kinds are moist, unctuous, and brown. Manna liquifies 
in moist air, dissolves readily in water, and, by the assistance of 
heat, in rectified spirit. On inspissating the watery solution, the 
Manna is recovered of a much darker colour than at. first. From 
the saturated spirituous solution, great part of it separates as the 
liquor ceols, concreting into a flaky mass, of a snowy whiteness, 
and a very grateful sweetness.” 
Manna is well known as a gentle purgative, so- mild in its 
operation, that it may be given with safety to children and preg- 
nant women; in some constitutions however it produces trouble- 
some flatulencies, and therefore requires the addition of a suitable 
aromatic, especially when given to an adult, where a large dose 
is necessary; it is therefore usually acuated by some other 
cathartic of a more powerful kind. The efficacy of Manna is said, 
by Vallisnieri, to be much promoted by cassia fistularis, a mixture 
of the two purging more than both of them separately; it is there- 
fore very properly an ingredient in the electuarium e cassia. 
4 
No. A8.—von. 4. 13 
