504 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the various structures. Delicate tissues such as muscle, nerve, connec- 

 tive tissue, etc. quickly become blue, while the ground substance of 

 cartilage, bones, etc. retain the red and violet for a longer period. An 

 advantage of this stain is that it does not colour the celloidin of celloidin 

 sections. 



Employment of Fat Stains for Differentiation in Preparing 

 Museum Specimens.* — R. H. Malone has employed fat stains in the 

 preparation of museum specimens with good results, especially in the case 

 of breast tumours, pancreas, and degenerated heart-muscle. The tissues 

 are hardened in 10 p.c. formalin for one or two days, the excess of 

 formalin washed off and the tissues transferred to a saturated solution 

 of Scharlach R in 70 p.c. alcohol for two hours. Large quantities of 

 staining fluid should be used, as the penetrative powers of the stain are 

 very weak. The specimen is then washed and differentiated in a 

 saturated solution of bichloride of mercury. The organ is then mounted 

 in 5 p.c. formalin. This method is particularly good for showing 

 up the " tabby-cat " striation of fatty degeneration of heart-muscle. 

 Counterstaining with alum-hfematoxylin will be found helpful in 

 differentiating normal breast tissue from tumour growth : — stain with 

 Scharlach R as above, counterstain with hematoxylin for one minute, 

 wash and transfer to lithium carbonate (saturated solution) until the 

 tumour is pale blue. 



(5) Mounting-, including' Slides, Preservative Fluids, etc. 



Mounting of Diatoms in Realgar.f — Chapman Jones says, " My 

 attention was first directed a few years ago to the particular subject 

 indicated by the title above! when I wanted a slide or two of the 

 smaller diatoms mounted in realgar. Slides of this kind were included in 

 the li^ts of all firms that deal in microscopical slides, but no one could 

 supply me, and I was told that the individual who prepared theui, after 

 poisoning himself by the process, had made up his mind to have nothing 

 more to do with it. It seemed to me that this was a highly unsatis- 

 factory position for so valuable a means of investigation, and I began to 

 look about . . . hoping to find some medium, or more than one, of 

 high refractive power that should be workable without risk of poisoning 

 by the microscopist who is -not a chemist. 



" Some objects need to be rendered more transparent for microscopical 

 examination that their dark details may be made visible . . while 

 others that are thin and transparent . . . are advantageously arranged 

 so as to render the detail as conspicuous as po-sible. Thus in photo- 

 micrography we need media of various refractive powers. 



" It will simplify matters if we limit our consideration to diatoms 

 prepared in the usual way so that only the siliceous skeletons of them 

 remain . . . stated to have a refraction index of 1*43. Diatoms are, 

 therefore, fairly visible in air (" dry "), with its refraction index of 1*0. 

 In water, refraction index 1 33, they are less visible, and some of the 



* Journ. Path, and Bact., xix. (1914) pp. 102-4 (1 pi.). 



+ Journ. Roy. Photo. Soc, Jan. 1914. 



t " On Media of High Refractive Power for Photomicrography." 



