INVERTEBEATA, CRYPTOGAMIA, MICROSCOPY, ETC. 



613 



added, and tlie excess must be neutralized by cautious addition of 

 ammonia. 



After staining, the sections must be rinsed in alcohol, not in water: 

 also if the solution be too strong it must be diluted with alcohol, as 

 water precipitates the carmine. 



4. Purpurin. — About as much purpurin as will lie on the point of 

 a knife is boiled in 50 c. c. of glycerine, the latter may be concen- 

 trated, or may have a little water added to it. The resulting orange- 

 red fluorescent solution is allowed to stand for two or three days, and 

 is then filtered. Unlike Eanvier's solution of purpurin, it may be 

 kept for months without precipitation. 



All the above fluids are stated to be quite permanent in the case 

 of balsam jjreparations : if glycerine is used as the mounting fluid it 

 should be slightly acidulated. 



Dr. Seller's Staining Processes.*^Dr. Carl Seller, continuing the 

 l)aper which we referred to at p. 329, gives the details of two pro- 

 cesses, which he has found to be so universally successful that he has 

 discarded all others. 



The first is a simple carmine solution (published by Dr. J. J. 

 Woodward in the ' Lens '), and is made as follows : — 



Best carmine (No. 40) gr. xv. 



Borax 5i. 



Water fl. .^vss. 



Alcohol (95 per cent.) fl. ^xi. 



Mix and filter, dissolve the crystals in 8 ounces of distilled water, 

 and evaporate over a water bath to 4 ounces. 



Sections placed in this fluid will become stained very evenly in a 

 few seconds, and be of a violet red when removed. They are then 

 immersed in a solution of 



Hydrochloric acid 1 part. 



Alcohol 4 parts. 



until they assume a bright rose colour, which appears in a very few 

 seconds. The sections are then well washed in several changes of 

 alcohol, after which they are ready for mounting. 



A specimen thus treated exhibits only the nuclei with the granules 

 stained, while the cell-contents and fibrous tissue are not tinted. 

 This is, in many cases, of great advantage, as a much clearer picture 

 results than if the colouring matter is also seen in the non-nucleated 

 structures, and the nuclei are marked only by a deeper staining. If, 

 however, for purposes of diagnosis, it is desirable to stain the con- 

 tents also, this can be accomplished by using a concentrated solution 

 of oxalic acid in alcohol, or by employing a very weak solution of 

 hydrochloric acid after the specimen has been stained. 



The second is a double staining with carmine and indigOn The 

 sections are first stained with carmine as described above, care being 

 taken to wash all traces of acid out of the tissues ; they are then im- 

 mersed in a solution of two drops of sulphindigotate of soda solution 

 in one ounce of 95 per cent, alcohol, which should be filtered before 

 * 'Am. Quart. Micr. Journ.,' i. (1879) p. 220. 



