202 INTERNAL ANATOMY OF INSECTS. 



by which means the vessels become firmer and stronger. 

 The parts of pupcs become much more distinct if they 

 are boiled for a few minutes : and the same mode may 

 be adopted in the examination of spiders. 



The most convenient mode of proceeding, which was 

 that also of Lyonet, is to dissect the insect in water, or, 

 to avoid putridity, in diluted spirits, if small, upon a 

 concave glass, to which it should be fastened by means 

 of a little melted wax; if larger, in the bottom of a com- 

 mon chip box, surrounded with a border of wax to re- 

 tain the fluid. The integuments of the insect, being 

 carefully divided longitudinally with scissors, should if 

 flexible be turned back, and fixed by small pins stuck in 

 by a fine pair of pliers, while the skin at the same time 

 is stretched by another. After making such observa- 

 tions as present themselves without further dissection, 

 the viscera must be cautiously extracted, washing away 

 the fat which surrounds them with spirits of turpentine, 

 in which it is soluble, applied by camel' s-hair pencils. 

 After separation they may conveniently be examined by 

 putting them into water, and gently shaking them so as 

 to cause the parts to unfold. If endowed with the pa- 

 tience of Swammerdam, you may even arrive at inject- 

 ing these minute parts with wax or coloured fluids, 

 conveyed by delicate glass tubes having one end as fine 

 as a hair, which he also employed to fill the viscera 

 with air; and afterwards drying them in the shade, and 

 anointing them with oil of spike in which a little resin 

 had been dissolved, he succeeded in preserving them. If 

 it is not convenient to finish the dissection of an insect 

 at once, it should be covered with spirits of wine. Swam- 

 merdam found a mixture of spirits and distilled vinegar 



