152 PllEPARATION 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 solidiby 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, aa 

 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 

 inicroscopist may find endless amusement or study in it. 

 From a single section the das* 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 J. 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. 



