52 THE MICROSCOPE. April 



tions was a contraction, evidently of the neuroglia in 

 various regions of the cord, especially of the white mat- 

 ter resulting in the formation of open spaces or cavities. 

 In the sections hardened in the 10 per cent solution 

 these cavities were so large as to destroy completely the 

 slides for microscopical purposes. In the 15 per cent 

 cord, the cavities were much smaller, but far more num- 

 erous, and the dorsal white columns looked like a honey 

 comb or sieve. This action of the formalin was mani- 

 fested in every section examined and is therefore not of 

 accidental, hut of regular occurrence. The draAvback of 

 the formalin in preventing the employment of the Pal 

 and Weigert methods of staining has been successfully 

 overcome by Marcus, who after hardening the cord for 

 from two to four weeks in a one-half per cent solution 

 of Formalin, places small portions one-half cm. thick in 

 Muller's fluid in a brood oven for seven days at a tem- 

 terature of 37° C. They are then dehydrated, imbedded, 

 and the cuts again placed in Muller's fluid, for from two 

 to seven days in a brood oven, quickly washed in alcohol 

 then transferred into the Weigert stain. 



The action of the formalin on the ganglion cells is a 

 happy one, swelling them and rendering their nuclei sus- 

 ceptible to very intense staining. 



The action of formalin on the brain has given very 

 fine results. Born succeeded in hardening the entire 

 brain very quickly for demonstrations, also small parti- 

 cles for microscopical purposes. I have been equally suc- 

 cessful and have some excellent specimens, nicely 

 hardened. I have not as yet tried any of the staining 

 methods on brains thus hardened and cannot state what 

 the results would be, although I have some specimens 

 under way. From my experience with Formalin I can 

 greatly recommend it, for the hardening of the various 

 organs and tissues for macroscopic as well as microscopic 

 purposes, but would still cling to the Muller's solution 



