76 Nervous Structures. 



NON-MEDULLATED NERVE FIBRE. 



This is best seen in a gold preparation of the tad- 

 pole's tail ; it will require a high power to trace the 

 finest fibres, Zeiss' E or F, but the one-twelfth oil im- 

 mersion of Powell and Lealand with the binocular will 

 enable the student to form a more correct idea of the 

 structures he is looking at and their relations to one 

 another. 



SPINAL CORD. 



Procure a fresh spinal cord of calf from the butcher 

 and cut it into pieces corresponding to the different 

 regions. Prepare one half of each of these pieces in a 

 2 per cent, solution of bichromate of potash, page 13, 

 and the other half in chromic acid mixture ; those pre- 

 pared in bichromate of potash may be put in as they 

 are, but those in chromic acid mixture must be cut into 

 lengths of about half an inch. The cord must be care- 

 fully handled care being taken not to squeeze it, and it 

 should be cut with a sharp razor. Transverse sections 

 of these must then be cut and stained with logwood, 

 some may be stained with anilin blue, page 29, others 

 double stained with carmine and indigo- carmine, page 37. 



Sections can be cut by the microtome, but the razor 

 must be very sharp and the cord well hardened. Very 

 thin sections can also be cut by the hand and each 

 section should be washed off the razor into spirit as 

 it is cut. This should not be done with a brush but 

 by dipping the razor into spirit. The cord prepared in 

 bichromate of potash will show the nerve structures, 

 that prepared in chromic acid mixture the neuroglia. 



