ON INSECT ANATOMY. 401 



along the length of the fibre, the muscle should be examined either 

 in living insects, or in recently removed parts immersed in blood 

 serum or some albuminous fluid (white of egg e.g.), or in glycerine, 

 but never in water. In insect muscle preserved in spirit, especially 

 if the insect has been dropped, while living, into the spirit, the 

 varying state of contraction of different elements of the same fibre 

 may be seen just as fixed at the time of death. 



It frequently happens that the anatomist has not the opportunity 

 of dealing with insects in the living or fresh condition. In such 

 cases the specimen must be preserved in weak alcohol. 



In the dissection of insects, different methods of treatment and 

 manipulation mast be adopted, according as it is desired to 

 learn the structure of any particular organ, or to prepare and mount 

 specimens, and economise so as to get the greatest namber of 

 preparations from a single insect. In learning the anatomy of any 

 insect, not previously studied, a few specimens must be sacrificed 

 by cutting and picking to pieces. But material may be saved by 

 following same methodical plan. External parts can of course be 

 studied as they present themselves, but it is worth while to preserve 

 the dermo-skeleton, either whole, or in parts (sections), and this is best 

 accomplished by boiling in solution of potash, then washing in cold 

 water and removing with scalpel or brush any remaining soft parts 

 (ligaments, membranes, tracheae, &c.). To mount them, a suitable 

 fluid, spirit, turpentine, balsam, glycerine, &c., must be used, and a 

 convenient size and shape of cell chosen. The parts composing the 

 mouth require special attention and should be separately mounted. 

 The whole head may be divided in various directions, yielding 

 longitudinal, transverse, and horizontal sections, each displaying 

 some particular aspect. Por example, a longitudinal section shews 

 external and internal lateral views of the cranium with eye, 

 antenna! first joint (the antenna being cut off) mandible, maxilla, 

 and palpi. Cross sections yield anterior and posterior views of the 

 internal processes, separating the cranial and facial halves. 

 Horizontal sections shew external and internal aspects of the vertex 

 of the cranium with orbital and antennal sockets, labrum, &c., or 



