Aug.. 1893. SOME USEFUL METHODS IN MICROSCOPY. 113 



Here they are left for an hour or two until completely stained. They 

 are then washed with water and brought up through the alcohols — 

 30 %, 50 %, 70 %, 90 %, and absolute — into oil of cloves, and then 

 mounted in Canada balsam. 



The above is the complete plan of procedure for this method. 

 Before, however, proceeding to describe its practical application to 

 the objects in question, a few words are necessary concerning the 

 agents mentioned. 



Hermann's fluid was, as its name implies, invented by Hermann^ 

 in his studies on nuclear division, etc., in the testis. It may be de- 

 scribed as a paraphrase, so to speak, of the well-known Flemming's 

 fluid (the second or strong solution) in which the i per cent, chromic 

 acid is replaced by i per cent, platinum chloride, thus : — 



Platinum chloride i per cent. ... ... 15 parts. 



Osmic acid 2 per cent. ... ... ... 4 >> 



Glacial acetic ... ... ... ... i part. 



I always make it up according to the following recipe : — Take 

 one of the ordinary sealed glass tubes containing a gramme of osmic, 

 as it is commonly sold, and break it in a bottle of a capacity of about 

 300 cc. ; then pour on it 50 cc. of pure distilled water, 12-5 cc. of 

 glacial acetic, and 200 cc. (more accurately i87*5 cc.) of a i per cent, 

 solution of platinum chloride. Shake the contents of the bottle up 

 together and put it aside. By the next morning the osmic will have 

 dissolved and the mixture will be ready for use. 



Alum carmine is too well-known a staining fluid to every zoologist 

 to require description here ; but the very valuable carmine stain 

 recently invented by Dr. Paul Mayer, 3 to which he has given the 

 name of Carmalum (" Carmalaun "), may not be so familiar to the 

 majority of English zoologists. The essence of his discovery consists 

 in using the pure colouring principle, carminic acid, instead of com- 

 mercial carmine. Carminic acid can be obtained from Dr. Grubler 

 in Leipzig at the rate of about four marks for ten grammes. Having 

 obtained the carminic acid, the method of making up the staining 

 solution is exceedingly simple, and can be carried out as easily in the 

 domestic kitchen as in the well-equipped laboratory, thus: mix to- 

 gether in a suitable vessel one gramme of carminic acid, ten grammes 

 of ammonia alum, and 200 cc. of distilled water. Heat the mixture up 

 to about boiling point, until the ingredients are dissolved, and then, 

 after cooling, carefully pour off or filter the liquid, which is now ready 

 for use. A small crystal of thymol or some other antiseptic should be 

 added, in order to keep it free from organisms. Carmalum is a dark- 

 red liquid with great staining powers, having especially the great 

 advantage that, like picrocarmine, it will give a beautiful stain to 

 objects that have been fixed in pure osmic acid, which alum carmine 

 will not do. It tinges the protoplasm slightly as well as the nucleus, 



2 ArcJt.f. Mikroskop. Anat. Bd. xxxiv. (1889), pp. 58-60. 

 ^Loc. cit. 



