XVII,-. Wilson: A ncw System ot" obtaining ilirecting-iuarks. 177 



paratioii oi' tlic block or duriiig sectioniug, aiid their axcs are to all 

 intents aiul piirposes as accuratel}^ perpeudiciilar to tlie plane of 

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

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

 tliat, on the same principle, directing filaments may be introduced 

 into celloidiu bloeks; but experiments in tliis direetion are not yet 

 completely carried out. 



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

 very fair alternative to the method described in this paper woiild 

 consist in using the Born-Peter plate with the grooves on the npper 

 surface as described by these authors 5 previously, however, laying 

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

 are utilised in the metliod 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 ensured. Two (ore more) of the ridges produced in 

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

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

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

 necessary, since the superimposition of the outlines of the sections 

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

 hand 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.] 



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



