ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 471 



tion, the writer gives an historical review of the application of micro- 

 chemical methods of staining, giving special attention to the carmine- 

 pigments. The earliest experiments on microscopic staining with 

 carmine for the purpose of a ready differentiation of tissues were 

 made by Goeppert and Cohn. More extended investigations on the 

 capability of the various elements of vegetable tissues to fix carmine 

 shortly followed by E. Hartig. In animal histology, carmine 

 staining was first employed by Gerlach (1858), Further contributions 

 to its application were made especially by Maschke, Thiersch, Beale, 

 Eollen, Gwancher, Hoyer, Czokor, Eanvier, and others. Reference is 

 further made to the cultivation of cochineal, and to the most con- 

 venient methods of obtaining carmine for technological purposes, and 

 its application as a staining material in the form of ammonium car- 

 ininate, and carmine acetate. The author convinced himself by ex- 

 periments that old preparations of ammonium carminate, which contain 

 a certain quantity of ammonium carbonate, stain better than fresh 

 solutions. Finally, a shorter reference is made to the aniline-dyes, 

 hsematoxylin, indigo-carmine, and picro-carmine. 



The second part includes a chronological and tabular account of 

 the literature of the subject, especially with regard to the following 

 staining materials : — (1) carmine; (2) hgematoxylin ; (3) ammonium 

 molybdate ; (4) alizarin and purpurin ; (5) alcanna and lakmus ; (6) 

 sodium indigo-sulphate (indigo-carmine). 



Mode of announcing new Methods of Reaction and Staining.* 

 — E. Giltay calls attention to the fact that the publication of new 

 methods of reaction is often made without sufficient precision for 

 others to be able readily to form a judgment on their applicability 

 for the special purpose. In the description of the application 

 of a reagent, at least one mode of preparing it ought to be accu- 

 rately described, such expressions as " somewhat," " a little," " a 

 short time," and such like, should be avoided, and replaced by exact 

 statements of weight and time. In the case of little known sub- 

 stances, the chemical formula — intelligible in all languages — should be 

 appended. The descriptions of colours should be as correct as 

 possible, with reference to all influencing circumstances, and should 

 be based on some definite colour-scale, such as that of Chevreul's 

 'Des Couleurs.' 



Pure Carminic Acid for Staining.f — G. Dimmock has often won- 

 dered why naturalists use carmine solutions in which water, with some 

 caustic or destructive material added, is the principal solvent. 

 Carmine of commerce, it is true, is not readily soluble, even in water, 

 until ammonia, borax, or some other aid to solution is added ; but car- 

 minic acid, the basis of the colouring matter of carmine, has long been 

 stated in the leading chemical dictionaries and handbooks to be 

 readily soluble in water and in alcohol. Watts (Diet. Chem., 1872, 

 1st suppL, p. 413) says of carminic acid: — " This acid forms a purple 



* Zeitschr. f. Wiss. Mikroekopie, i. (1884) pp. 101-2. 

 t Amer. Natural, xviii. (.1884) pp. 324-7. 



