CHAPTER VIII. 



CUTTING AND MOUNTING MICROSCOPIC SECTIONS, 

 AND MOUNTING INSECTS WHOLE. 



AFTER becoming familiar from careful dissections with 

 the gross or general anatomy of insects, and having per- 

 ceived the relations of the various viscera to one another 

 and to the walls of the body, the student is prepared to 

 appreciate serial microscopical sections of insects, or of 

 selected portions of their bodies. These can be made by 

 the aid of the microtome, and an insect whose integument 

 is not too thick can with this instrument be cut from head to 

 tail into several hundreds of slices from y-^o- to J-^Q^ of an 

 inch in thickness. In this way the histology or fine anatomy 

 of the hypodermis, and the epidermal glands of the nervous 

 ganglia, alimentary canal, the crop with its teeth, the 

 stomach and intestine, etc., can be examined. 



The following directions, which apply to soft organs, or 

 portions of them, of animals in general, have been taken 

 from Lee's " Microtomist's Vade Mecum,"* while extracts 

 from other authors, relating to special points, are added. 



In order to prepare sections of entire insects, or of sepa- 

 rate organs, the insect to be studied should be first carefully 

 killed, and the tissues "fixed," then stained, finally washed 

 out or dehydrated with alcohol, and sections cut with the 

 microtome and mounted in balsam or glycerine jelly. 



In general, larvae and other soft-bodied insects should be 

 killed by being thrown into weak or 50 per cent alcohol, 

 so that the body or the separate soft parts will not contract 



* A. B. Lee's "Microtomist's Vade Mecum" (London, 1885). See 

 also Whitman's excellent " Methods in Microscopical Anatomy and 

 Embryology" (Boston, 1885), Prudden's "Histology, "and especially 

 Stohr's "Lehrbuch der Histologie." 



