214 
PROGRESS OF MICROSCOPICAL SCIENCE. 
examples of nerve insertion under the sheath of the muscle, and 
distribution of its terminal filaments in the muscle substance. 
Fragments of gland structure sometimes offer unexpected yet 
beautiful specimens for preparation. .The same may happen with 
varieties of gland in mucous membrane of intestines and other organs 
(testis, urinary tubes, hepatic tubes, &c.). Beautiful varieties of fatty 
tissue and dermoid tissues or exquisitely striated muscle (as in the 
coats of the dorsal vessel) or curious forms of tracheal ramification 
and wonderful networks distributed over or penetrating through other 
tissues may be secured as chance prizes, if looked for amongst the 
debris after the principal organs have been secured. 
The dissection and removal of the soft organs and finer structure 
is however attended with considerable difficulty when enclosed in a 
casing of such tough and resistant 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 oesophagus and intestine. In 
the instance of the cricket, however, the intracranial portion of the 
oesophagus, with its closely adherent infra and supra-oesophageal 
ganglia, cannot be detached without first cutting 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, longi- 
tudinal 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 
preserve them in unchanged position under the action of the knife. 
The following plan, which has been found most successful in making 
sections of diseased structures, and is employed by Professor Ranvier, 
appears to me the most suitable for the purpose. 
Place the parts (or the whole insect, taking care to make such 
punctures or slits in the integuments as will allow the fluids used 
to penetrate thoroughly) in alcohol for twenty-four hours, a time 
sufficient to fix, without contracting the tissues. Then, in solution 
