124 



THE MICROSCOPIST. 



chese will become visible. These vessels, naturally filled with 

 air, are of a beautiful metallic white color, which produces a 

 very pretty effect upon the darker grounds of the other organs 

 upon which they run. The stomach and intestinal canal, if 

 large and transparent, will exhibit the minute ramifications of 



Fig. 35. 



the tracheae the best ; for this purpose, after being slit open 

 and well washed, they should be either mounted in fluid or be 

 placed on a slide to dry. If care be taken in the mounting, 

 they will show very well in balsam. When the entire tracheal 

 system is required to be dissected from the larva of an insect, 

 all the viscera should be taken out ; the main trunks with their 

 tufts of branches, will then be seen running down on either 

 side of the body, and if care be taken in the dissection, the 

 whole system may be removed from the cavity, and laid out, 

 or rather floated on, a slide to dry, previous to being mounted 

 in balsam. The spiracles require very little dissection. They 



