ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 517 



repeating the process a beautiful blue of any desired tone was easily- 

 imparted to the membrane. If the plant had not been damaged by the 

 above treatment, the bluish colour disappeared in a few hours, the Berlin 

 blue was decomposed, and the iron remained. By putting the plant in 

 a solution of ferrocyanide of potash acidulated with hydrochloric acid, 

 the blue could be restored to its original situation. 



Roux's Colour-test for the detection of Gonococcus.* — Dr. E. C. 

 Wendt's researches on gonococcus were merely intended to find a 

 diagnostic criterion for gonorrhoea. He therefore examined other secre- 

 tions as well, e.g. balanitis, otorrhoea, conjunctivitis, &c. Gonococci 

 were found in all cases of gonorrhoea, but in other cases, even in the 

 normal urethra, there were found diplococci indistinguishable from the 

 gonorrhoea cocci. The criterion insisted on by Bumm, namely the 

 intracellular arrangement of the gonococci about the nucleus, is found 

 by the author to be not always correct, since it is not the case where 

 blenorrhoea is passing away. The only certain characteristic, according 

 to the author, is that from Eoux's test, which depends on the fact that 

 the gonorrhoea bacteria are able to retain anilin to a slight extent. 



Acid Logwood Stain.f — An excellent acid logwood stain can, it is 

 stated, be made as follows : — One part of a saturated solution of calcium 

 chloride in proof spirit (alcohol of 50°) is added to eight parts of a 

 similar solution of alum. Extract of logwood (the common commercial) 

 is added to the mixture and agitated until it no longer dissolves freely. 

 Let the container stand in a cool, quiet place for a few days, decant the 

 clear liquid (which makes an excellent stain just as it is), and to every 

 100 parts add 80 parts of a 1 per cent, aqueous solution of acetic acid. 

 Let stand for a day or two, and filter off into a glass-stoppered vial. 



Alcoholic Alum-Carmine Stain.^— Dr. W. C. Borden gives the 

 following formula for producing a perfectly clear purplish-red fluid, 

 superior to any aqueous alum-carmine stain in clearness and brilliancy of 

 colouring. It will keep indefinitely, but a slight precipitate sometimes 

 forms which should be filtered out. This does not indicate any decom- 

 position of the stain, nor does it alter its staining character in any 

 respect. Cochineal (whole insects), 1 dr. ; saturated solution of alum, 

 4 oz. ; 95 per cent, alcohol, 4 oz. Pulverize the cochineal in a mortar, 

 add the saturated solution of alum, and boil for fifteen minutes, adding 

 distilled water occasionally during the boiling to make up for the water 

 lost by evaporation. Cool and pour without filtering into a ten-ounce 

 or larger bottle. Add the alcohol and let stand, with occasional shaking, 

 for forty-eight hours. Filter and preserve in a close-stoppered bottle. 



The following stain made with carmine and without heat will give a 

 fluid nearly identical with the first, except that no precipitate occurs, 

 however long it be kept. Carmine, 30 gr. ; alum, 4 dr. ; distilled water, 

 4 oz. ; 95 per cent, alcohol, 4 oz. Grind the carmine and alum together in a 

 mortar, gradually adding the water. Add the spirit and pour without 

 filtering into a ten-ounce bottle, cork tightly, and let stand for a week, 

 shaking occasionally. Filter, and preserve in a close-stoppered bottle. 



For staining in bulk, pieces of tissue may be transferred directly from 

 strong spirit to either fluid, and may remain from two days to two weeks. 



* Med. News, i. (1887) pp. 455-7. 



t St. Louis Med. and Surg. Jouru., liv. (188S) p. 1C5. 



J The Microscope, via. (1888) pp. 83-5. 



