PREPARATION OF HARD TISSUES. 205 



to the cabinet-maker as the silver grain; and at e is a 

 magnified view of a part of the same: the woody fibres 

 are seen with their dots I, and the horizontal lines k indi- 

 cating the medullary rays cut lengthwise ; whilst at c is a 

 tangental section, and fa, portion of the same magnified: 

 the openings of the medullary rays mm, and the woody 

 fibres with vertical slices of the dots, are seen. Very 

 instructive preparations may be made by cutting oblique 

 sections of the stem, especially when large vessels are 

 present, as then the internal structure of the walls of some 

 of them may oftentimes be examined. The diagram above 

 given refers only to sections of a pine ; all exogenous stems, 

 however, will exhibit three different appearances, according 

 to the direction in which the cut is made ; but in order to 

 arrive at a true understanding of the arrangement of the 

 woody and vascular bundles in endogens, horizontal and 

 vertical sections only will be required. Specimens of 

 wood that are very hard and brittle should be first 

 softened by boiling in water ; and as the cutting-machine- 

 will answer for other structures besides wood, it should 

 be understood, that horny tissues will also be softened 

 by boiling, and can then be cut very readily. 



Preparation of Hard Tissues. All sections of recent and 

 greasy bones should be soaked in ether for some time, and 

 afterwards dried in the air, before they are fit for the saw, 

 file, and hone ; by dissolving out the grease, the lacunas 

 and canaliculi show up very much better. When it is 

 wished to examine the bone-cells of fossil bone, chippings 

 only are required ; these may be procured by striking the 

 bone with the sharp edge of a small mineralogical-hammer: 

 carefully select the thinnest of the chips, and mount them 

 at once, without grinding, in Canada balsam. If desirable 

 to compare bone structures, it must be borne in mind that 

 the specimens for comparison should be cut in one and the 

 same direction ; as the bone-cells, on which we rely for our 

 determination, are always longest in the direction of the 

 shaft of the bone, it follows that if one section were trans- 

 verse, and the other longitudinal, there must be a vast 

 difference in the measurement of the bone- cells, in conse- 

 quence of their long diameter being seen in the one case, 



