CHAPTER XIII. 147 



239. Haematein is found in commerce as a brown powder, entirely, 

 though with difficulty, soluble in distilled water and in alcohol, 

 giving a yellowish-brown solution, which remains clear on addition 

 of acetic acid. Alkalies dissolve it with a blue- violet tint. (See 

 also last edition.) 



240. Iron Haematoxylin, Generalities. This method is due to 

 BENDA (Verli, Phys. Ges., 18851886, Nos. 12, 13, 14 ; Arch. Anat. 

 Phys., 1886, p. 562 ; third ed. of this work, p. 365). 



The method was independently worked out about the same time 

 by M. HEIDENHAIN. 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 mordant in Benda's liquor 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 differentia- 

 tion. 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 recommends 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 GIBSON'S picro-saurefuchsin has been recommended as a 

 differentiation fluid by Benda (DeutscJi. med. Wochenschr., 1898, 

 No. 30). I find it gives very delicate differentiations, 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 stain, 

 not hcematein, the iron salt oxidising it into haematein. or into a 

 higher oxidation product. I have obtained some good stains with 



102 



