78 Neurological Technique 



the required serial sections by the following simple device' : 

 Keep the d|isks of tissue in the order in which they were cut 

 previously to placing them in the osmic acid mixture (B) and, in 

 mounting them on the block in thick celloidin preparatory to 

 hardening, pile the disks in their order one upon another and 

 harden the whole as one piece. If mounting directly on the 

 wooden block proves difficult, the pieces may be arranged in a 

 paper box filled with thick celloidin, and the whole hardened 

 and afterward fastened on the block for sectioning, the paper 

 having been removed. Then section and mount serially ; throw 

 nothing away. 



Results similar to those obtained by the Marchi method 

 have been obtained from material fixed in formalin. ° Pieces of 

 tissue (3-5 mm. thick) are taken from material preserved in 10 

 per cent, formalin (X, A, p. 63) and placed for 5—7 days in a 

 mixture containing i gram of osmic acid, 3 grams of the iodate 

 of sodium (Nalj), and 300 cc. of distilled water. 



The pieces may then be washed, dehydrated, and imbedded 

 in paraffin or celloidin in the usual way. 



It is claimed that sharper contrast is gained in this way 

 than by the original method of Marchi, from the fact that the 

 normal tissues are more colorless. 



The sodium iodate must have the same effect on the medul- 

 lary sheath as does the chromic salt in Marchi's method, for 

 normal medullary sheaths fixed in formalin will blacken in 

 osmic acid. 



' A. HocHE, " Ueber secundare Degeneration, speciell des Gowersschen Biindels, 

 e\.c." Archiv f. Psychiatrie,Bi. XXVIII, 1896. 

 'BUSCH, Zeit.f. wiss. Mik., Bd. XV, 1899. 



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