150 PREPARATION AND MOUNTING 
To obtain a true knowledge of the structure of bone, 
sections must be cut as in wood, both transversely and 
longitudinally ; but with fossil bones, without the lapidary’s 
wheel, it is a laborious task, and indeed can seldom be 
properly accomplished. In this place, also, it may be 
mentioned that by submitting bone to the action of muriatic 
acid diluted ten or fifteen times with water, the lime, &, is 
dissolved away and the cartilage is left, which may be cut 
into sections: in caustic potash the animal matter is got 
rid of. Both of these preparations may be mounted in 
fluid. 
The method of cutting thin sections of bone may be also 
employed with the stones of fruit, vegetable ivory, and such 
like substances; many of which show a most interesting 
arrangement of cells, especially when the sections are trans- 
verse. Most of these objects present a different appearance 
when mounted dry to that which they bear when i balsam, 
owing to the cells becoming filled; and to arrive at a true 
knowledge of them we must have a specimen mounted in 
both ways. 
Some will perhaps remark that most of the directions for 
section cutting are given to those who are totally without 
artificial power, and must rely upon their own manual exer- 
tions. I reply that these hints are mostly given to such ; 
but Mr. Butterworth’s directions to use the lathe are so 
ample, that a repetition of them at the mention of each class 
of “ sectional” substance would be mere tautology. 
To those who study polarized light, few objects are more 
beautiful than sections of the different kinds of horn. We 
will briefly inquire into the best method of cutting these. 
There are three kinds of horn, the first of which is hard, 
as the stag’s, and must be cut in the same manner as bone. 
The second is somewhat softer, as the cow’s. The third is 
another and still softer formation, as the “horn” (as it is 
termed) of the rhinoceros. In cutting sections of the two 
last we should succeed best by using the machine invented 
for these purposes,. which I shall shortly describe when the 
