HiEMATEIN (h^EMATOXYLIn) STAINS. 165 



platinum. The product is not of perfectly constant quality. It ought 

 to dissolve easily in water or alcohol, and the solution should not 

 become turbid on addition of acetic acid ; if it does, it is over-oxidised. 



240. Iron Hsematoxylin, Generalities. — This method is due 

 to Benda [Verh. Phys. Ges., 1885— 1886, Nos. 12, 13, 14; 

 Arch. Anat. Phys., 1S86, p. 562 ; third ed. of this work, p. 365). 



The method was independently worked out about the same 

 time by M. Heideniiain. The method is almost universally 

 practised in the form given by Heidenhain, not on account 

 of any essential difference between the two, for there is 

 none, but chiefly because Heidenhain has given more precise 

 instructions concerning the process. 



After carefully comparing Heidenhain's process with 

 Benda's later process (next §), I find that the two give an 

 absolutely identical stain ; that is to say, that if you mor- 

 dant in Benda's Kqucr ferri, next §, and differentiate in the 

 same, you will get exactly the same effect as by mordanting 

 in ferric alum and differentiating in the same. But you may 

 vary the results somewhat by varying the differentiation. 

 Benda has pointed out {Verb. Anat. Ges., xv, 1901, p. 156) 

 that you may differentiate either by an agent which simply 

 dissolves the lake — such as acetic or hydrochloric acid ; or 

 by an oxidising agent, such as chromic acid, or the liquor 

 ferri or the ferric alum. The former^ he thinks, are the 

 best for the demonstration of nuclear structures, the latter 

 for cytoplasmic structures. For these he greatly recom- 

 mends Weigert's borax-ferricyanide mixture, as being the 

 easiest and safest to employ. 



For myself, I find that differentiation in the iron salt 

 (§ 241 or § 242) is sufficient for almost all purposes. Acetic 

 acid of 30 per cent, acts much too quickly to be safe, and 

 causes swelling of the tissues. 



Van Gieson's picro-siiurefuchsin has been recommended 

 as a differentiation fluid by Benda {Deutsch. med. Wochen- 

 tchr., 1898j No. 30). I find it gives very delicate differ- 

 entiations, but acts very slowly, requiring nearly as many 

 hours as the iron alum solution does minutes. The addition 

 of the saurefuchsin to the picric acid is, I find, not necessary, 

 and may prove an injurious complication. 



In these processes hsematoxylin is generally used for the 



