238 



J. W. GROVES ON SECTIONS OF ANIMAL TISSUES. 



With some — as Logwood, Gold Chloride, and Silver Nitrate — this 

 is of the utmost importance. 



Those stains which colour all tissues alike are of little use unless 

 employed as a ground to bring out details which would be left 

 untouched by a selective stain, which can afterwards be used, and 

 then their value cannot be over-rated. 



Thus Molybdate of Ammonia produces a most delightfully cool 

 blue-grey general stain, which in no way interferes with the sub- 

 sequent use of carmine, when all the nuclei appear pink on a pleasant 

 neutral tint ground. 



To obtain this a five per cent, neutral aqueous solution of the 

 molybdate should be used. The stain is complete in 24 hours, at 

 an ordinary temperature and under the action of light. 



Specimens thus coloured become brown by supplementary expo- 

 sure to the action of tannic acid (1-15) or pyrogallic acid (20 

 per cent.). 



Another general stain is a strongly ammoniacal solution of 

 carmine, but this is of little use, and is best avoided. 



Eosin, again, is a general stain, which may be used either before 

 or after the sections have been coloured with logwood. One part 

 of eosin should be used with 1,000 of water. 



Many of the other stains, too, which are themselves selective, 

 may be used with others which have a still stronger selective 

 power, and thus for the time appear to be merely general stains. 

 In this way may be used — 



Carmine and Logwood, 

 Carmine and Silver Nitrate, 

 Logwood and Silver Nitrate, 

 Logwood and Gold Chloride, 

 And some others. 



Selective Stains. 



Of these none is more useful or more pleasant to work with than 

 logwood ; but it is not so commonly used as carmine, because 

 many find it difficult to prepare, and others, from want of success 

 in its use, in consequence, I fancy, of hardening their material in 

 fluids containing chromic acid or bichromates of too great strength. 



There are two useful formulas for the preparation of logwood 

 solutions — 



1. Kleinenberg's modified by Golding Bird is easy to use, while 



