ON INSECT ANATOMT. 403 



penetrating through other tissues may be secured as chance prizes, 

 if looked for amongst the debris after the principle organs have been 

 secured. 



The dissection and removal of the soft organs and finer structure 

 is however attended with considerable difficalty when enclosed in a 

 casing of such tough and resistent chitin integument as forms the 

 dermo-skeleton of Coleoptera, Orthoptera, Hymenoptera and other 

 classes. Of course this difficulty is greatest at the natural cinctures 

 which mark the chief divisions of the insect into head, thorax and 

 abdomen, and wherever internal processes connect the anterior and 

 posterior surfaces, as happens for instance in the case of the cricket, 

 both in the head and the thorax. The abdominal organs are easily 

 removed from almost every kind of insect, but their continuity with 

 the parts contained in the thorax can be preserved only by skilful 

 manipulation. As the alimentary canal, and nerve chord, extend from 

 head to tail, the integument must be slit up from end to end on 

 the ventral side, but not directly in the median line, because it is 

 best to remove the ganglionic chord with the sesophagus and 

 intestine. In the instance of the cricket however the intra- cranial 

 portion of the sesophagus, with its closely adherant infra — and 

 supra-cesophageal ganglia, cannot be detached without first catting 

 off the head and very careful tearing out, as these organs rest upon 

 a saddle-shaped osseous plate in the very centre of the cranial 

 cavity. The ganglionic chord within the thorax is also enclosed 

 between forks of internal osseous plates, but by following it up 

 from the abdomen where it lies free, it can with a little care be got 

 out entire. It is best to keep the whole insect floating in glycerine, 

 the body being secured in any convenient way in a fluid-holding 

 cell of suitable form. 



To exhibit continuous systems of organs, and show their relative 

 position to the several divisions of the external integument, 

 longitudinal and transverse sections are useful. But these cannot 

 be well made without a preparatory hardening process. If complete 

 sections of the whole body are desired, the hardening process should 

 be supplemented by soaking the parts in some material which will 



