152 PREPARATION AND MOUNTING 
the outer “ casing,” and the inner substance somewhat re- 
sembling the pith of plants. | 
It would be out of place to enter into the description 
of the different forms met with; but the ways in which 
sections are to be procured may be noticed. If transverse 
sections are required, some place a quantity of hairs betwixt 
two flat pieces of cork, which by pressure hold them firmly 
enough together to allow the required portions to be cut 
with a razor. Others take a bundle of the hairs and dip 
it into gum or glue, which gives it when dry a solidity equal 
to wood. Sections of this are then cut with the machine 
mentioned a little further on, and these may be mounted in 
balsam. The human hair is easily procured in the desired 
sections by shaving as closely as possible a second time and 
cleansing from the lather, &c., by carefully washing. Most 
hairs, however, should be examined both transversely and 
longitudinally. It is not difficult to procure the latter, as 
we may generally split them with the aid of a sharp razor. 
In a great number of hairs there is a quantity of greasy 
matter which must be removed by soaking in ether or some 
other solvent before mounting. 
We may next consider the best method of procuring 
sections of wood, which must be cut of such a degree of 
thinness as to form transparent objects, and so display all 
the secrets of their structure. There is no monotony in 
this study, as the forms are so various, and the arrange- 
ment of the cells and woody fibre so different, that the 
microscopist may find endless amusement or study in it. 
From a single section the class of trees to which it has 
belonged may be known, often even when the wood is fossil. 
The apparatus best adapted for cutting these sections is 
made as follows:—A flat piece of hard wood, about six 
inches long, four wide, and one thick, is chosen, to which 
another of the same size is firmly fixed, so as to form, in 
a side view, the letter T. On one end of the upper surface 
is fastened a brass plate, perfectly flat, in the centre of which 
a circular opering is cut about half an inch in diameter. 
