542 SUMMARY or CUBKENT RESEARCHES RELATING TO 



all the properties of ordinary carmine except in being of a dark violet 

 colour. Over this the author is not so enthusiastic as over the next two 

 solutions where he has substituted chrome alum for potash alum in the 

 formulas given by Czokor and Grenacher for making alum cochineal 

 and alum carmine. The ingredients are mixed in the exact propor- 

 tions as given by Czokor and Grenacher. The mixture is then left 

 in an oven at the temperature of about 70° 0. for 24 to 48 hours. 

 When cold the liquid is filtered. 



Both fluids are of a violet colour, and both stain nuclei perfectly. 

 The author gives the palm to the cochineal stain. Preparations may 

 remain in this solution for more than 24 hours without becoming 

 diffusely stained. If the preparations are to be preserved in resinous 

 media it is necessary to wash carefully in water, otherwise the alum 

 chromate, which is insoluble in water, is precipitated on the surface of 

 the section as brownish needles. A special advantage of this cochineal 

 chromate solution is that it keeps well for an indefinite period with- 

 out the addition of any preservative agent. Another advantage is 

 that the nuclei assume a violet colour closely resembling that given 

 by hgematoxylin. 



Modification of Arcangeli's Carmine Stain.* — M. P. Francotte 

 finds that in Arcangeli's first formula f 50 cgrm. carmine is too much, 

 and proposes the following modified formula, which is based on the 

 solubility of boric acid in alcohol. Alcohol at 90, 75 ec. ; distilled 

 water 25 cc. ; boric acid 5 grm. ; carmine 40 cgrm. This mixture is 

 boiled for fifteen minutes, and a beautiful red alcoholic solution is 

 obtained on filtration. 



Staining the Central Organs of the Nervous System. J — Prof. 

 C. Golgi, after some strictures on gold chloride methods (which he 

 condemns because neither the manner in which the interlacement 

 of the fibres takes place, nor the different parts which contribute to 

 their formation, are demonstrated) states that whatever success he has 

 had is due to the three following methods : — 



1. Method of black staining obtained by treating specimens 

 successively with potassium or ammonium bichromate and silver 

 nitrate. 



2. Method of the successive action of a mixture of osmic acid and 

 potassium bichromate followed by silver nitrate. 



3. Method of the combined action of potassium and ammonium 

 bichromate and perchloride of mercury (by transmitted light the 

 colour is apparently black ; by direct light, a metallic white). 



By the method of the combined action of bichromate of potash 

 and of nitrate of silver, the black staining is obtained as the result 

 of two operations. Pieces of nervous tissue about a centimetre square 

 are hardened in a 2 per cent, solution of bichromate, or in Miiller's 

 fluid. The strength of the bichromate may be gradually increased 

 from 2 to 5 per cent. In any case, this fluid should be frequently 



* Bull. Soc. Belg. Micr., xii. (1886) pp. 48-51. 



t See this Journal, v. (1885) p. 1094. 



X Arch. Italiennes de Biologic, vii. (1886) pp. 15-47. 



