438 NERVOUS SYSTEMSPECIAL METHODS. 



spinal cord of adult subjects, 2 per cent, should be preferred. For 

 the reduction he uses Cajal's hydroquinone-formalin mixture, taking 

 care in further recutting the pieces, before transferring them into 

 the reducing fluid, so that their thickness should not exceed 2 mm. 

 He dehydrates and embeds pieces, preferably in paraffin, or he makes 

 sections by the freezing method. He usually tones these by means 

 of 0-2 per cent, gold chloride, fixes with 5 per cent, sodium hypo- 

 sulphite, counterstains and mounts as usual. 



The method gives good results also with material from lower 

 vertebrates and invertebrates.* 



849. Other Methods and Modifications. BESTA (Anat. Anz., 

 xxxvi, 1910, p. 477) fixes for two days in 20 parts of formol with 2 

 of acetic aldehyde and 80 of water, washes for twenty-four hours in 

 distilled water changed seven or eight times, and puts for two days 

 in 4 per cent, solution of ammonium molybdate, makes paraffin 

 sections, stains in a 1 : 1000 solution of thionin, differentiates in 

 3 parts of creosote to 1 of absolute alcohol, and passes through pure 

 creosote and xylol into neutral balsam. Recommended for Purkinje 

 cells and spinal ganglia of young animals. 



SUCHANOW (Neurol. Gentrbl., xxi, 1902, p. 777) has obtained good 

 results by the use of Golgi-Veratti mixture, keeping pieces of spinal cord 

 and spinal ganglia for twenty to thirty days in the mixture and for two 

 to three days in the rejuvenating fluid. 



LEGENDKE (Anat. Anz., xxxvi, 1910, p. 209) omits the toning and 

 bleaching by Golgi's arsenious acid method, and embeds in paraffin. 



Similarly COLLIN ET LUCIEN, Bibliogr. Anat. Supp., 1909, p. 238. 



SAVAGNONE (Pathologica, i, 1909) silvers pieces fixed in Golgi's arse- 

 nious acid mixture with 30 c.c. of tachiol (10 per cent, silver fluoride) 

 in 100 of water. 



CAKLETON (Journ. E. Micr. Soc., 1919, p. 321) reduces pieces treated 

 according to Cajal's uranium nitrate method for only two hours in the 

 usual hydroquinone mixture. 



PENFIELD (Brain, xliii, 1920) has successfully employed Cajal's 

 uranium nitrate method for his experimental investigations on the 

 alterations of Golgi's apparatus in nerve cells of spinal cord and 

 spinal ganglia of young cats. He adds 20 c.c. (instead of 15) to 

 Cajal's fixing fluid and as much as 1-5 grms. of sodium sulphite to 

 the hydroquinone-formalin solution. He finds it imperative to 

 dehydrate pieces very quickly before embedding them in paraffin. 

 In order to obtain perfect fixation of the spinal cord he sometimes 

 performs a laminectomy in the lower lumbar region of the ansesthe- 



* Da Fano's method has been used by me with great success for the 

 study of gametogenesis of many invertebrata (J. B. G.). 



