NISSL. GRANULES 4G9 



cations, to whicli due attention was paid when preparing the 

 following account. 



The Nissl method is extremely useful for the study of nervous 

 tissue under physiological and pathological conditions ; it stains, 

 when properly carried out, not only the tigroid substance and 

 the basophil parts of the nuclei of nerve-cells, but also the nuclei 

 and part of the cytoplasm of neuroglia cells as well as connective 

 tissue elements normally or abnormally present in the nerve- 

 tissue. In a somewhat modified form it has been largely and 

 successfully employed for investigating the topographical dis- 

 tribution of nerve-cells (cyto-architecture) in different regions of 

 the central nervous system of man and animals, 



1001. Nissl's Methylen-blue Method. Not too small pieces of 

 fresh tissue are fixed in 96 per cent, alcohol and hardened therein 

 for a few days. They should not be allowed to fall to the bottom 

 of the bottle, but kept floating by means of some filter paper or 

 cotton-w^ool. The alcohol must be in large quantity in proportion 

 to the number of pieces, and repeatedly changed. The pieces 

 are cut without imbedding, and the sections collected in 96 per 

 cent, alcohol, from which they are directly floated on some stain 

 filtered into a watch-glass at the moment of using it. The 

 stain should be at least three to four months old, and shaken at 

 the moment of filtering the quantity needed. It is prepared by 

 carefully dissolving 1-75 grm. of Venetian soap in 1 litre of dis- 

 tilled water and then adding 3-75 grm. of methylen blue (B 

 patent). It is a good practice to shake the bottle vigorously 

 from time to time, and to refilter into it the stain left in the 

 watch-glass after staining one or more sections. 



The watch-glass containing the stain with the section floating 

 on it is warmed carefully over a flame until small bubbles rise 

 to the surface. The section, which should not have fallen to 

 the bottom of the watch-glass, is immediately transferred into 

 a mixture of 10 parts of anilin oil and 90 parts of 96 per cent, 

 alcohol, and as soon as no more colour is given off (if often takes 

 only some seconds), it is lifted on to a slide, pressed with smooth 

 filter paper, and cleared with a few drops of pure anhydrous 

 cajeput oil. Care should be taken not to dry the section exces- 

 sively with the filter paper and to pour the cajeput oil on to the 

 section very quickly. The cajeput oil not only clears the section, 

 but stops the differentiation ; it is, therefore, advisable to renew 

 it after a little while on the section. As soon as this has become 

 quite transparent, the cajeput oil is dried off with filter paper, 

 the section thoroughly washed with benzol and covered with a 

 drop of thick xylol-colophonium, rendered more fluid by passing 

 the slide carefully over a flame, and quickly covering the section 

 with a thin cover-glass before the colophonium sets again by 

 cooling. 



