818 
THE PRINCIPLES OF BOTANY. 
Oak bark for tanning is a valuable article of commerce, so 
much so that we have ere now obtained more for the bark 
stripped off felled oak than for the timber. Oak bark is 
employed for medicinal use in both schools, and the follow¬ 
ing succinct description of “ Quercus cortex” and its uses, in 
Tuson’s f Veterinary Pharmacopoeia,’ will not be out of place 
here:—The dried bark of the small branches and young 
stems of Quercus pedunculata collected in spring from trees 
growing in Britain. 
“ Composition. —Its medicinal activity depends upon its 
containing fifteen to twenty per cent, of tannic acid, with a 
small quantity of gallic acid. 
“ Characters. —Covered with agreenish shining epidermis ; 
cinnamon-coloured on the surface, fibrous, brittle, and strongly 
astringent. 
“ Actions and Uses. — Internally : astringent and tonic. 
Employed to arrest diarrhoea, dysentery, and similar mucous 
discharges. Externally: astringent, styptic, and excitant. 
Occasionally used for stimulating unhealthy wounds and 
arresting gangrene, also in prolapsus recti and prolapsus 
uteri. 
“ Doses. —Horse, 2 to 6 drachms. Cattle , 2 to 6 drachms. 
Sheep , \ to 2 drachms. Pig , \ to 2 drachms. Dog , 10 to 
30 grains. 
“ Modes of Application. — Internally : The powdered bark 
made into a bolus, or mixed with gruel, but preferably in the 
form of Decoctum Quercus. Externally : The powder or 
Decoctum Quercus. 
<f Preparation.— “ Decoctum Quercus.” 
But there can be little doubt that the most active remedial 
agent will be found in nut-galls, speaking of which the author 
just quoted states that— 
“ Their therapeutic properties are chiefly due to their con¬ 
taining about twenty-six per cent, of tannic acid, H 3 C 27 H ly 0 17 , 
with a trace of gallic acid, H 3 C 7 H 3 0 5 . Aq. This gallic acid 
has been used in photography, and it is the well-known basis 
of ink.” 
As regards galls, it should be stated that within the last few 
years our English or native oak has been attacked by an 
insect before altogether new to us, of which a gall is formed, 
which we have tracked in its spread from Devonshire, where 
it was first observed, from the west into Dorset, Wilts, Glou¬ 
cester, to the East Coast, and since then into North Wales; 
in fact, it now seems to be pretty general. These galls are 
due to the Cynips quercus petiolati, and it would appear that 
what would otherwise be leaves is converted into these excre- 
