ZOOLOGY AND BOTANY, MICROSCOPYj ETC. 673 



C4) Staining and Injecting'. 



Double-staining of Nucleated Blood-corpuscles.* — Dr. W. M. Gray 

 gives tlie following directions :- -Spread a thin layer of blood on a 

 clean slide, and dry; immerse the slide in a beaker of alum-carmine 

 (Grenadier's formula) for five minutes ; wash in clean water, and im- 

 merse in a beaker of a weak solution of sulphindigotate of soda or 

 potash (the solution should be of a dark-blue colour, not black-blue as 

 in a strong solution). After the slide has acquired a purplish hue, wash 

 in water and dry. After drying, warm slightly and mount in balsam. 

 The nuclei will be a beautiful red, and the protoplasm a greenish blue. 



Staining Nerve-endings with Gold Chloride. | — In his new researches 

 on motor nerve endings, Dr. W. Kuhne gives the following as the best 

 methods for manipulating gold chloride ; — 



(1) Lowit's method, sometimes to be followed by strong formic acid, 

 is especially useful, as thin muscles need not be dissociated. 



(2) First, 1/2 per cent, formic acid, gold chloride 1 per cent., then 

 equal parts of a mixture of glycerin and water, to which 1/4 to 1/5 

 volume formic acid has been added. Specially useful for muscle of 

 warm-blooded animals. 



(3) Same as (2), but without preliminary acidulation. For cold- 

 blooded animals. 



(4) Golgi's method. 1/2 per cent, arsenious acid, 1/2 per cent, 

 gold chloride of potash, then 1 per cent, arsenious acid, and reduction in 

 sunlight. Useful for all objects. 



(5) Modification of 4, consists of laying the strips of muscle in a 

 mixture of 1/2 j)er cent, arsenious acid, 1/4 per cent, gold chloride of 

 potassium, and • 1 per cent, osmic acid, then 1 per cent, arsenious acid, 

 and reduction in sunlight. Best suited for reptiles. 



With regard to the rest of the preparation, the author says that the 

 finer dissociation should be effected at the most favourable stage of the 

 hardening, therefore always in the gold solution. Secondly, many small 

 bits of muscle (ten to twenty from 1-2 mm. broad) should be placed in 

 2-5 ccm. of the fluid, which should be allowed to act for different lengths 

 of time, then in the gold solution from four to thirty minutes ; from the 

 reduction fluid they are to be removed, say hour by hour, and transferred to 

 unacidulated dilute glycerin. In Golgi's method the separate portions 

 were transferred to fresh arsenious acid in the dark when staining began. 

 In this way various degrees in the effects can be obtained. With the 

 exception of Golgi's all the methods are usually found to overstain, and 

 this has therefore to be removed. The effect of acid on nerve-endings 

 is always disadvantageous ; it is, therefore, a great advantage to produce 

 gold preparations without previous acidulation, and the acidulation stage 

 should always be shortened as much as possible. 



Preservation of preparations in dilute glycerin acidulated with formic 

 acid is not very favourable for details. Golgi's method, therefore, has a 

 great advantage in not employing glycerin, but mounting in balsam 

 after dehydration in absolute alcohol is perfectly suitable for showing 

 the stained nerve-endings. The certainty of the results varies with 



* Queen's Micr. Bulletin, v. (1888) p. 15. 



t Zeitschr. f. Biol., xxiii. (1887) pp. 1-148 (pis. A-Q). 



