Journal of Applied Microscopy. 609 



ical union with the hsematoxylin, and there is a higher oxidation product present 

 than haematein. Usually after treatment with iron the sections are put in a 

 haematoxylin solution till diffusely colored and then differentiated by an acid 

 mixture either in the iron mordant or else free. Many modifications of this 

 method are too well known to need description ; Heidenhain's the best perhaps. 

 A special process of his is to previously stain in Bordeaux red or anilin blue, to 

 prevent the iron from going into chromatin and plasma. To stain the cell 

 plasm I, Butschli brings the sections first into a weak solution of iron acetate, 

 then into the haematoxylin, and does not differentiate further. 



Hcematoxylin and Copper. — The principle of this combination is the same as 

 with the preceding metal ; a copper salt was used before in combination with or 

 after haematoxylin ; copper sulphate and copper acetate are both used, and in 

 a certain form this process constitutes the famous Weigert method. Weigert 

 hardens tissue in potassium bichromate, imbeds in collodion, and treats for 

 two to three days in a half saturate solution of copper acetate, following this 

 with a weak alkaline haematoxylin (f to 1 gr. haem., 10 gr. alcohol, 90 gr. water, 

 1 gr. concentrated solution of lithium carbonate) containing lithium carbonate, 

 which aids in the formation of haematein. He finally differentiates with his 

 potassium ferrocyanide solution weakened one-half. Many modifications of this 

 method have been made, but none have changed the principle of reactions. 

 Weigert himself uses as a mordant equal volumes of a concentrated solution of 

 copper acetate and a ten per cent, solution of potassium sodium tartrate, but 

 treats again with copper acetate before sectioning ; the hsematoxylin is of a 

 somewhat different composition, and weak acetic acid is used in differentiation. 



Hcematoxylin and Molybdenum. — This is used for nerve tissue by several 

 workers, and most simply by staining the tissues in an old mixture of haematoxy- 

 lin and ten per cent, phospho-molybdic acid (1 pt.), chloral hydrate (6 to 10 pts.), 

 and water (100 pts.). 



HcE7natoxyli7i and Vanadium, etc. — Objects are fixed in potassium bichromate 

 and copper sulphate in fifty per cent, alcohol, cut in collodion, and the sections 

 mordanted in a mixture of one part • of ten per cent, solution of vanadium 

 chloride and four parts of eight per cent, aluminum acetate, treated with a copper 

 haematoxylin, and differentiated in hydrochloric acid alcohol. Axis cylinders, 

 ganglion cells, etc., are stained, and sheaths not. Which of the four metals, 

 aluminum, chromium, copper, or vanadium, plays the most important part, is 

 not known. 



Hcematoxylin with Other Metals. — Heidenhain found magnesium, strontium, etc., 

 useless, other authors believed themselves to have demonstrated the presence of 

 calcium carbonate in egg yolk by the use of haematoxylin ; results are not yet 

 final. Hermann uses an alcoholic haematoxylin and differentiates by Pal's 

 modification of Weigert's method, using sodium hypermanganate in the mordant, 

 but since the tissue is hardened in platinum chloride and osmic acid, the metal 

 acting is not clearly known. Other metals have been used, zinc, bismuth, 

 cobalt, nickel, tin, uranium, wolfram, but are not in common use. 



HiEMATEiN. — This can be used alone as a stain for the cell nucleus, mucous 

 substances, and nerve fibrils ; according to Mayer this is due to the union of 



