16 THE FIXATION OF NERVE FIBRES. 



per cent, formalin solution show numerous little lines which run 

 through the myelin in an irregularly radial direction. When viewed 

 longitudinally, the appearance is that of a fine network, the so- 

 called neurokeratin network. 



This network is much more distinct and regular than that seen 

 in the myelin of nerve fibres, which, for example, are fixed in 

 Mliller's fluid. It is w^ell shown by staining with Weigert's 

 haematoxylin, or with iron-alum haematoxylin. By either of these 

 methods the network is stained black, while the spaces between 

 the meshes are colourless and appear empty. 



When stained by either of these methods, the fibres, as seen 

 in cross section, are of a somewhat different appearance from that 

 already described, for, instead of the lines running through the 

 myelin, black bands are seen with white spaces between them. 



Osmic acid stains the network (of the formalin hardened 

 substance) a faint brown. 



The appearance of nerve fibres hardened in formalin is the 

 same whether teased, stained, or mounted in glycerin, without the 

 use of alcohol, or soaked in alcohol and ether, as for celloidin 

 embedding. 



When nerve fibres (also tissues from the central nervous system) 

 are stained by Weigert's method after formalin fixation, the reduc- 

 ing fluid should be diluted from five to ten times with water, 

 otherwise the decoloration will be too rapid and uneven. 



From the results above described it would appear that formalin 

 is a valuable addition to the list of reagents for the fixation of 

 nerve fibres. 



The Cebus and the Matches. — Prof. E. D. Cope, writing 

 to the American Naturalist, says : — " A Cebus apella in the Phila- 

 delphia Zoological Garden has become an expert in striking 

 matches. He distinguishes the end with the fulminate, and I 

 have not seen him make an error in this point. He seizes the 

 match at the proper distance from the fulminate and so avoids 

 breakage. He uses for friction the rough side of a kettle which is 

 used for water, and spends no time on the glazed surface. As 

 soon as the match is lit he throws it away, and I have not seen 

 him burn himself. No man could handle the match more appro- 

 priately. He does not, however, always select a proper surface, 

 as he tried on one occasion to strike a match on my finger 

 without success." 



