Objects for the Microscope. 103 



And whilst looking at the thorax of this little Beetle, as 

 hereafter we may look at that of a Fly, it will not lessen 

 pur pleasure to be reminded of the many kinds of muscles 

 that worked unerringly the will of this small creature. It 

 had its levator muscles for raising its limbs ; depressors, 

 antagonistic to these, for depressing them ; flexors for bend- 

 ing the joints ; extensors for unbending or extending them ; 

 abductors for drawing an organ backward, and abductors 

 for drawing it forward ; constrictors that contract a body or 

 an opening as in breathing; laxators that relax it. All 

 these are in quick action in the little insect that runs over 

 your hand or escapes from your eye ; all these have been 

 planned and attached, and the numbers so accurately inter- 

 woven, that they work without hindrance or confusion by 

 the creative word of the Most High. 



As the head for sensation, with its ganglion and branch- 

 ing nerves, and the thorax for locomotion, so the abdomen, 

 usually in nine segments, is appointed as the digester of 

 food and the organ of generation. 



The internal parts of an insect cannot be seen in these 

 preparations. We must therefore confine our attention 

 to the external anatomy, and, before this slide is put away, 

 examine the wing. 



The wing of a Beetle should be compared with that of a 

 Fly, in order to appreciate its peculiar structure. The 

 substance is membranous, double and joined together by 

 canals or nervures, through which the blood circulates a 

 tracheal vessel runs, and a nerve, branching from the 

 thoracic ganglion, and giving off innumerable fibres to 

 groups of vesicles situated immediately beneath the costal 

 nerve. This is only seen with very high powers and good 

 glasses ; also requiring a particular preparation of the wing. 

 It must simply be soaked in turpentine for a week or more, 

 and mounted in balsam warmed just enough to receive the 

 wing, when the tracheal vessel, the nerve, and the vesicles, 

 may be distinctly seen with a good -in. or J-in. object 

 glass. 



That strong nerve on the forepart of the wing is the 

 costal nerve. As the Beetle's wing is folded under the 



