248 QUERCUS ROBUR 



astringent matter, and is more easily separated from the wood 

 than at any other period of the year. In practice, however, in this 

 country, the usual time of barking is from the beginning of May 

 to about the middle of July ; and the process is as follows : The 

 barkers make a longitudinal incision with a mallet furnished with 

 a sharp edge, and a circular incision by means of a barking bill. 

 The bark is then removed by the peeling irons ; the separation 

 being promoted, when necessary, by beating the bark with the 

 square end of the mallet. It is then carefully dried in the air by 

 setting it on what are called lofts or ranges, and is afterwards 

 stacked. 



General Characters and Composition. Oak bark is usually found 

 in pieces of from one to two feet long, and it varies very much 

 in appearance according to the age of the stem or branch from 

 which it has been obtained. The bark of the small branches and 

 young stems, which is alone official, occurs in quills which are 

 usually about a tenth of an inch or less in thickness. It is nearly 

 smooth externally, and of a shining silvery or ash-grey colour, 

 variegated with brown. Internally it is cinnamon-coloured or 

 brownish-red, and longitudinally striated. The fracture is 

 fibrous and tough ; its taste very astringent ; and its odour is 

 very feeble except when moistened, when it resembles tan. The 

 bark of old stems is in thick, more or less flattened pieces, which 

 are very rough externally from the presence of numerous deep 

 cracks and wrinkles. It is very inferior in its medicinal 

 properties to the young bark, and should not be substituted 

 for it. 



The most important constituent of oak bark is a peculiar kind 

 of tannic acid, which was first noticed by Stenhouse in 1843, and 

 then proved by him to be different from the tannic acid of nut- 

 galls ; it is termed querci-tannic acid, and according to Neubaer 

 it exists in young oak bark in the proportion of from 7 to 10 per 

 cent. A solution of gelatine is precipitated by an aqueous 

 solution of oak bark ; and the latter solution becomes dark blue 

 or purple on the addition of perchloride of iron. A solution of 

 tartarated antimony causes no precipitate with a watery solution 



