900 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Preparations may be mounted in glycerin or in balsam, and arc very 

 permanent. The author has exposed objects frequently to the light 

 in the course of the year, and has not noticed any loss of colour. 



This method is especially suitable for nervous tissue and for 

 ossifying cartilago, and may also be recommended for the examination 

 of glands and glandular organs. 



Watney's Double Stain with Hematoxylin.* — Dr. W. Krause 

 recently reproduced f a procedure introduced by Watney J for double 

 staining by the exclusive use of hamiatoxylin. This is effected by 

 successive staining with a strong red and a weak blue solution. The 

 difference between the two solutions really depends on the quantity 

 and acidity of the alum. An intense blue is obtained by the use of 

 freshly prepared dry alum ; the red colour appears when acid has 

 gradually become free in the alum, but best when the quantity of the 

 alum solution is less than three times the quantity of the wood-extract. 

 Connective tissue, the protoplasm of the connective-tissue corpuscles, 

 and the walls of vessels are stained red. Mucus, almost all nuclei, 

 and lymph corpuscles, are stained blue. 



A communication from Prof. Langhans to Dr. M. Flesch shows 

 that this double stain takes place more simply if Delafield's hfema- 

 toxylin be used in the ordinary way, and the preparations when 

 mounted in Canada balsam are exposed to the light for a long time. 

 Preparations mounted in glycerin are said to undergo this change. 



Silvering Diatoms. § — In an article on " Photography in Belgium," 

 an account is given of Dr. H. van Heurck's method of photographing 

 AmpMpleura pellucida and other diatoms, with a description of the 

 apparatus || and processes employed. The method of silvering the 

 diatoms, for the purpose of making their details more perceptible, is 

 also described. 



The cleansed valves scattered over a disc of cover-glass are 

 silvered, glass and all, with a silvering solution consisting of nitrate 

 of silver 10 parts dissolved in 6*2 parts of strong liquid ammonia; 

 after solution, 50 parts of distilled water are added, and the 

 liquid is filtered ; after filtration 800 parts of distilled water are 

 added ; this forms solution A. Solution B consists of 2*25 parts of 

 tartaric acid previously exposed for a long time to sunlight ; the acid 

 is then dissolved in 8' 5 parts of water. These solutions are mixed, 

 drop by drop, with violent shaking, and after sufficient of B has been 

 added to A to tend to produce a permanent precipitate, the silvering 

 solution is made. The pieces of glass and diatoms to be silvered are 

 placed upon the flat cover of a vessel containing boiling water, which 

 water is kept at that temperature during the silvering operation, 



* Zeitschr. f. Wiss. Mikr., ii. (1885) p. 353. 



t Internat. Zeitschr. Anat. u. Histol., i. (1884) p. 154. Infra, p. 906. 



% Phil. Trans., iii. (1882) p. 1075. 



§ Engl. Mech., xlii. (1880) pp. 548-9, from Brit. Journ. of Photography. 



|| Swan incandescent electric lamp ; Weuham's radial arm Microscope, and 

 Nachet's large inverted Microscope with silvered mirror (principally) ; Zeiss's 

 objectives ; Powell's oil condenser. 



