208 THE AMEEICAN MONTHLY [September, 



TECHNIQUE. 



Hsematoxylin as a means of ascertaining the Alkalinity or 

 Acidity of Tissues. — Prof. F. Sanfelice has found that the acid or 

 alkaline reaction of tissues may be recognized by staining with Boeh- 

 mer's haematoxylin (alkaline) , or with the author's iodized hasmatoxylin 

 (acid). 



In using this method as a test, two principal precautions must be ob- 

 served : First, it is necessary that the normal reaction of the tissue must 

 not be interfered with, hence reagents such as chromic acid and its salts, 

 Midler's fluid, and Flemming's solution are unsuitable fixatives. The 

 author used chiefly absolute alcohol for hardening and fixing, and also 

 corrosive sublimate, the excess of which must always be carefully ex- 

 tracted with spirit. The second precaution is that the haematoxylin 

 solution must have only a feeble reaction. 



Among the instances of differential staining obtained by this method 

 it is mentioned by the author that the protoplasm masses in the ovary 

 and testicle of Selachians are colored red when the whole of the tissue 

 is treated with the alkaline solution — a fact which proves that the ele- 

 ments undergoing this form of necrobiosis acquire an acid reaction. 

 Goblet-cells in the intestinal mucosa become colored blue, while the 

 rest of the tissue remains red. Hence the reaction of goblet-cells is 

 alkaline, and this method might be usefully employed to ascertain the 

 reaction of tissues or elements, and their products. — yourn. de Mi- 

 crographies xiv (1890), pp. 21-22. J. R. M. S.^ 1890, p. 538. 



Ne-w Method of Staining Central Nervous System, and its 

 Results. — Prof. P. Flechsig recommends the following method of 

 staining the nerve-cells of the cerebral cortex and their prolongations. 

 By means of it it was shown that the axis-cylinder process was the 

 only prolongation from the cell which was in connection with a nerve- 

 fibre ; that the axis-process, which is not at its commencement medul- 

 lated, divides like a T, i. e.^ dichotomously at a right angle. In the 

 occipital lobe a trichotomous subdivision was the rule, although fre- 

 quent subdivision was also remarked. In the neighborhood of the 

 central fissure some axis-fibres did not subdivide. 



These results were obtained by hardening pieces in 2 per cent, 

 aqueous solution of chromate of potash, and then making sections not 

 exceeding j^^^ mm. in thickness. 



After soaking in 96 per cent, spirit, the sections are kept for 3 to 8 

 days in a solution of redwood extract at a temperature of 35° C. The 

 sections having been washed in distilled water are then decolorized in 

 the following manner : Each section is placed in 3 ccm. J to -\ per cent, 

 solution of permanganate of potash until the solution has lost its bluish 

 color ; it is then immersed in the decolorizer (distilled water 200, oxalic 

 acid I, hyposulphite of potash i), until all traces of yellowness have 

 departed from the section. 



The redwood solution is made as follows : i gram of the pure extract 

 of Japan redwood is dissolved in id grams of absolute alcohol, and then 

 diluted with 900 grams of distilled water. To this are added 5 grams 

 of a saturated solution of Glauber's salt and a similar quantity of a satu- 

 rated solution of tartaric acid. 



