XVII, 2. Wilson: A new systcrn of obtaining direeting-marks. 177 



paration of tbe block or diiriug sectioning, and their axes are to all 

 intents and purposes as acciirately perpendicular to the plane of 

 section as are tlie coloured ridges of tlie directing plane of the 

 paraffin block prepared by the Born-Peter method. 10) It is obvious 

 that , on the same principle, directing filaments may be introdiiced 

 into celloidin blocks; but experiments in this direction are not yet 

 completely carried out. 



For those who already possess a Borx-Peter grooved plate, a 

 very fair alternative to the method described in this paper would 

 cousist in nsing the Born-Peter plate with the grooves on the upper 

 surface as described by these authors ; previously, however, laying 

 in two or niore of the grooves such fine prepared nerve-strands as 

 are utilised in the method above described, and melting them down 

 in the grooves prior to embedding. If the embedding bars are so 

 placed as to overlap the ends of the grooves a little, the retention 

 of the Strands in the grooves during the process of embedding will 

 be absolutely eusured. Two (ore more) of the ridges produced in 

 Casting a Born-Peter block will then each contain a solid core con- 

 sisting of a blackened nerve-bundle, and the subsequent processes 

 of coloration of the ridges and the directing plane are rendered un- 

 necessary, since the superiraposition of the outlines of the sections 

 of the nerve-strands amply suffice for directing marks. On the other 

 band the directing marks are necessarily more remote from the em- 

 bedded object than if the method described in the foregoing pages 

 were foUowed. 



Sydney, New South Wales, 12th. February 1900. 

 [Eingegangen am 15. März 1900.] 



Zeitscbr. f. wiss. Mikroskopie. XVII, 2. 12 



