CELLS.— RAPHIDES. 
45 
East Indies twenty-five per cent., and the English or 
that sold in the streets by men dressed as Turks, ten per 
cent. Buyers of this drug usually judge of its quality 
by its grittiness, that is, by the quantity of raphides it 
contains, and this is the more curious, as the crystalline 
matter cannot from its nature, contribute to the activity 
of the drug, since the tincture which contains no 
raphides, is as efficacious as the powder. Certain plants, 
of the Cactus tribe, seem to be almost entirely made up 
of raphides ; in some instances every cell of the cuticle, as 
shown in Fig. 27, B, contains a stellate mass of crystals; 
while in others, the whole interior is full of them, 
rendering the plant so exceedingly brittle, that the least 
touch will occasion a fracture. On this account, some 
specimens of Cactus senilis , said to be one thousand 
years old, which were a few years since sent to Kew 
Gardens from South America, were obliged to be packed 
in cotton, with all the care of the most delicate jewellery, 
to preserve them during the transport. Raphides of 
peculiar figure are common in the bark of many trees. 
In the hiccory, Carya alba , masses of flattened prisms, 
having both extremities pointed, 
may be observed ; similar crys- 
tals are present in the bark of 
the Lime-tree , and in Fig. 29 
they are represented in situ; 
Prismatic raphides in the hark they occur in rows, their pointed 
of the Lime-tree . , . 
extremities nearly touching each 
other, their principal situation being in the cellular tis- 
FIG. 2 . 9 . 
