494 



New York Academy of Sciences. Biological Section. 



Jan. 14th, 1895. 



Notes on neurological methods and exhibition of photo- 

 mi cr ogr aph 8. 



A paper on The Use of Formalin in Golgi's Method, was 

 read by Mr. 0. S. Strong. The writer found that formalin (40 *'/q solution 

 of formaldehyde) may be used (instead of osmic acid) mixed with po- 

 tassium bichromate. Pieces of adult brain were placed in the following: 

 potassium bichromate (3 V2 % — 6 %) 100 volumes -|- formalin 2^/3 to 5 vol. 

 During several days or more the tissue is transferred to the silver ni- 

 trate bolution (I Yo)- Or the tissue after 1 to 2 days may be transferred 

 from the above bichromate-formalin mixture to the following pot. bich. 

 (5 %) 2 vols. + formalin 1 vol. After 12 to 24 hrs. the tissue is put into 

 the silver solution. The advantages of this method are that 

 it avoids the use of osmic acid and that the stage of har- 

 dening favorable for impregnation lasts longer than when 

 the osmium-bichromate mixture is used and good results are 

 consequently more certain. In other words, the formalin-bichromate does 

 not overharden. In this respect it is al«o superior to the lithium 

 bichromate method of the author (N. Y. Acad, of Sc. Pro. Vol. XIII, 1894). 

 For embryonic tissue the formalin method is probably not equal to the 

 osmium-bichromate method, possibly because it does not harden suffi- 

 ciently. For such tissue lithium bichromate (which hardens more 

 rapidly than potassium bichromate) had better be mixed with the formalin 

 instead of potassium bichromate. While good results are obtainable, 

 especially with advanced embryonic tissue, with either of the above, yet 

 the author believes that for such tissue the osmium-bichromate method is 

 probably in certain respects somewhat superior. 



A fuller account will be published later. 



Dr. Iba Van Gieson reproted some preliminary observations on the ac- 

 tion of formalin as a fixative and preservative of the central nervous 

 system for the ordinary histological staining methods : solutions of for- 

 malin, four, six, and ten per cent, were used, followed, by 95 % alcohol, 

 and celloidin embedding. Sections of the human cord, cerebellum and 

 cortex prepared in this way gave very thorough fixation of the ganglion 

 cells, neuroglia cells, and fine nerve fibres. 



Weigert's haematoxylin method can be applied to such sections and 

 gives very good results for the plexus of fine fibres in the cortical and 

 spinal grey matter. The myelin of the fine fibres is well preserved and 

 gives the characteristic bluish black reaction with the Weigert haemato- 

 xylin stain, as in chrome hardened preparations. The background of 

 the grey matter is especiülly clear and the fibres sharply delineated. The 

 formalin hardened sections should be soaked in the neutral copper acetate 

 Bolution, diluted one half with water, for 2 hours, then thoroughly washed 

 in water and immersed in the Weigert lithium -carbonate haemato- 



