T. C. WHITE ON INSECT DISSECTION. 37 



witli the sternal surfaces and carefully slit up tlie integument, repeat 

 the process on the opposite side of the body, and then raise it by 

 holding it with the forceps and clearing away its attachments with 

 the needle, you will then not disturb any of the subjacent visceral 

 organs, but will see them all in situ. Having noticed their re- 

 lations one to the other, proceed to isolate them by clearing away all 

 the tracheal attachments with two needles — -a blunt one and a sharp 

 one — and if done with a steady hand and a keen look out, no very 

 great difficulty will be experienced in unravelling what before seemed 

 a tangled labyrinth. It is sometimes a good plan after removing 

 the integument from the sternal surface to place your subject in 

 glycerine and water, and to leave it for 24 hours ; but in this matter 

 I would leave the matter to every man's own judgment, for some- 

 times I have found very good results arise from the simple dissection 

 under plain water. We must bear in mind that we are working on 

 tissues of great delicacy, and will do well to observe two precautions. 

 Your instruments must be perfectly free from roughness, either aris- 

 ing from patches of rust or burrs left after sharpening. I have often 

 experienced great annoyance after making a delicate dissection that 

 has consumed perhaps a couple of hours, and have taken up a 

 flattened needle to it, and not detected some roughened spot till it 

 has caught some of the fine fibres of my work, and then all was a 

 hopeless mass of entanglement. Again in dissecting out the nervous 

 distribution in insects the nerves will be found very fragile, and will 

 scarcely bear the strain put upon them in clearing them from the 

 surrounding tissue ; but the addition of a little alcohol to the fluid 

 under which they are being dissected will harden them, and so pre- 

 vent their rupture. This I have found a very useful agent in carry- 

 ing out dissection; it comes in in all cases most advantageously, 

 enabling you to isolate many organs, that without its aid would 

 collapse and become, to coin a phrase, a mass of inextricability. 



The medium I have generally found most suitable for mounting 

 specimens of insect dissection in has been glycerine. Nothing has 

 shown them up to greater advantage, and I should recommend that 

 in preference to anything else, as it maintains their transparency, 

 while other preservative fluids make them dense and discoloured. 



With these few remarks I must close this short paper, hoping it may 

 induce some one to take up this subject, and not only produce plea- 

 sure in themselves but also add to our knowledge in this interesting 

 branch of biology. 



