444 E. A. MINCHIN ON SOME DETAILS IN THE ANATOMY OF 



laboratory at the Lister Institute, made some beautiful dissections 

 of the ventral nervous system of the flea, showing both thoracic 

 and abdominal ganglia in continuity. On the other hand, it is by 

 no means difficult to dissect out the abdominal chain in its whole 

 length, up to and including the large metathoracic ganglia, the 

 ganglia of the jumping legs. To do this the flea should be held by 

 the thorax with the pointed needle, while with the flat -edged needle 

 the abdominal segments are carefully detached and pulled off 

 from behind forwards successively, until only the thoracic segments 

 are left. If the operation has been successfully performed, and 

 the abdominal segments together with the contained digestive 

 and reproductive organs removed, the abdominal chain of ganglia 

 will be seen proceeding from, and adhering to, the hindmost 

 thoracic segment. With practice the complete severance of the 

 abdomen and its organs from the thorax can be effected with one 

 pull. 



Now take another slide and place on it a cover-slip (| inch 

 square). Place the slide and cover-slip on the stage of the dis- 

 secting microscope, put a quite small drop of salt-solution on the 

 cover-slip, and transfer the thorax of the flea from the slide on 

 which it was dissected to the small drop of fluid on the cover-slip, 

 and there proceed with the dissection. The big metathoracic 

 ganglion-mass can be seen quite plainly in the hindermost part 

 of the thorax, with the abdominal chain of ganglia proceeding 

 from it. With the needles the metathoracic ganglion must be 

 carefully dissected out and set free from the thorax ; this operation 

 is not at all difficult, though it requires both skill and practice to 

 dissect out the first two thoracic ganglia as well, in unbroken 

 continuity with the rest of the ganglionic chain. If during the 

 dissection the cover-glass slips about on the slide, it can be fixed 

 quite firmly by letting a tiny drop of distilled water run in between 

 cover-glass and slide, but I avoid this as a rule, because it makes 

 it difficult to get the cover-slip off later on. 



When the dissection has been completed, the fragments and 

 debris of the thorax should be removed and cleaned up as much 

 as possible, leaving the nervous system in the small drop of fluid 

 on the cover -slip. Now the cover-slip must be lifted carefully off 

 the slide and all superfluous moisture drained off it, so as to leave 

 the nervous system stranded on the cover-slip, as near the centre 

 as possible. The fluid can be drained off either by tilting the 



