336 NATURAL SCIENCE. may. 



two drops of the former to about lo c.c. of the latter. This method 

 is especially recommended for series of sections — ribbons — which are 

 slightly curved or crumpled, as the water causes them to flatten out, 

 while the amount of albumen present, though sufficient to make the 

 sections stick on, is too infinitesimal to be appreciably coloured by 

 the staining fluids. 



The chapter on staining is certainly one of the most valuable in 

 the book, and the portion dealing with the stains is divided into three 

 parts, headed respectively " Substantive," Adjective," and " Vital 

 Staining Methods." By "substantive staining methods" the author 

 denotes all processes where the staining fluid, as made up, acts 

 directly upon the substance to be stained. By " adjective staining 

 methods " are meant those processes in which the substance is first 

 treated with a mordant, used in a solution separate from the stain, 

 and not combined with it as in the ordinary combinations of alum 

 and other salts with carmine or hasmatoxylin, commonly employed in 

 laboratories. Among adjective staining methods are given the 

 famous hsematoxylin methods of Heidenhain and Weigert, as well as 

 a remarkable new method of the author's, in which the mordant used 

 is a solution of tannin and tartar emetic, followed by fuchsin, safranin, 

 or other anilines as a stain. This is the first time an adjective method 

 has been employed for an aniline stain, and it is said to give results 

 iboth curious and valuable. The ordinary staining reaction of the 

 aniline is, as it were, inverted; the fibres of the karyokinetic spindle, 

 for instance, are coloured, and not the chromosomes. The centrosome 

 is also said to be very distinctly shown in the resting cell. 



These adjective staining methods, first invented by Heidenhain, 

 .and since elaborated by him and by others, are among the most 

 valuable of modern microscopical methods, and Heidenhain's later 

 method with iron, alum, and haematoxylin is rapidly establishing itself 

 in zoological and embryological, as well as in histological, technique. 

 It may be especially recommended for showing micro-organisms in 

 • cells or tissues, not only in pathological material, but also in cases 

 where such organisms occur normally, as in Peloviyxa, for instance, 

 where this method shows the curious bacteria in sections with a 

 clearness not attained by any other stain. 



The various methods of staining intra vitam with methylene blue 

 form the third section of the chapter on stains. These important 

 processes are perhaps not treated with the fulness they deserve, and 

 the book has appeared just too soon for it to contain an account of 

 Bethe's method for fixing the methylene blue in the tissues, which is 

 of so great importance that it may be worth while to give a brief 

 account of it here, abstracted from Bethe's memoir on the nervous 

 ■system of Carciniis mmias in the Archiv. fur Mihroskopische Anatomie, 

 vol. xliv., p. 585 ; 1895. 



The stain is applied either by injecting the animals with it, or by 

 placing pieces of tissue in a weak solution. For injecting Crustacea a 

 li per cent, solution in normal saline solution was employed. For 

 fixing the stain in the tissues, the following solutions are used: — (i) P'or 

 vertebrates: Ammonium molybdate, i gr.; distilled water, 10 cc; H.jO^, 

 I cc. ; H CI, I drop. (2) For invertebrates : Ammonium molybdate, 

 I gr. ; distilled water, 10 cc. ; H2O2, i cc. 



The fixative should be used freshly made up, and during the 

 process of fixation should be surrounded by a freezing mixture. 

 Small objects are fixed for two to three hours, larger ones, up to 

 I cc. in bulk, for four or five hours. After fixation the objects should 

 be thoroughly washed in distilled water and dehydrated with alcohol, 



