204 



PREPABATION OF OBJECTS. 



Fig. 57. 



camel-hair pencils, or the handles of steel-pen-holders, will 

 answer extremely well), in such a manner that their points 

 should not project far,^ since they will otherwise have too much 

 "spring:" much may be done by their mere tearing action; but 

 if it be desired to use them as cutting instruments, all that is ne- 

 cessary is to give them an edge upon a hone. It will sometimes 

 be desirable to give a finer point to such needles, than they ori- 

 ginally possess ; this also may be done upon a hone. A needle 

 with its point bent to a right angle, or nearly so, is often useful; 

 and this may be shaped by simply heating the point in a lamp or 

 candle, giving to it the required turn with a pair of pliers, and 

 then hardening the point again by reheating it and plunging it 

 into cold water or tallow. 



106. Gutting Sections of Soft Substances. — Most important in- 

 formation respecting the structure of many substances, both 

 Animal and Vegetable, may be obtained by cutting sections of 

 them, thin enough to be viewed as transparent 

 objects. Where the substances are soft, no other 

 instrument is necessary for this purpose, than a 

 sharp knife, which may be best made with a thin 

 two-edged blade like that of a lancet ; conside- 

 rable practice is needed, however, to make effec- 

 tual use of it ; and some individuals acquire a 

 degree of dexterity, which others never succeed 

 in attaining. In cutting sections of Animal tis- 

 sues, which, owing to the quantity of water they 

 contain, do not present a suiSciently firm resis- 

 tance, it is often desirable to half-dry these, by 

 exposing small pieces freely to the air, with the 

 aid of a gentle warmth if required ; when this 

 desiccating process has been carried sufiiciently 

 far, thinner sections can be cut, than could pos- 

 sibly have been made in the original state of the 

 tissue ; and the texture, after a short maceration in water, almost 

 entirely recovers its pristine characters. There are certain tis- 

 sues, however, which will not bear to be thus treated, and of 

 which it is sufiicient to examine an extremely minute portion; 

 and for making sections of these, such a pair of scissors as is re- 

 presented in Fig. 57 will often be found very useful; since, 

 owing to the curvature of the blades,^ the two extremities of a 



^ The following is the mode in which the Author has found it convenient to mount 

 his needles for this and other purposes: — The needle being held firmly in =1 pair 

 of pliers grasped by the right haml, its point may be forced into the end of a cedar or 

 other stick held in the left, until it has entered to the depth of half an inch or more ; the 

 needle is then out oif to the desired length (the eye end being thus got rid of) ; and 

 being then drawn out, the truncated end is forced into the hole previously made by the 

 point, until it cannot be made to penetrate further, when it will be found to be very se- 

 curely fixed. The end of the handle which embraces it, may then be bevelled away 

 round its point of insertion. 



^ It is difBcult to convey by a drawing the idea of the real curvature of this instru- 

 ment, the blades of which, when it is held in front view, curve — not to either side — 



Curved Scissors for 

 cutting Thin Sections. 



