1056 SUMMARY OF OURKENT RESEARCHES RELATING TO 



partially dry the slide by resting it npon filter-paper before dropping it into 

 the alcohol-bath. The slide, which has remained in alcohol six minutes, is 

 brought again into distilled water for half a minute, since our colouring fluids 

 are water solutions. The hsematoxylin is then dropped upon the slide, and 

 removed again at the end of six minutes by resting the edge of the slide upon 

 filter-paper, and afterwards washing with distilled water for one minute. 

 The same process follows with the nigrosin and eosin, the first remaining 

 upon the slide for one minute, the second two minutes. From the eosin 

 we bring the preparation directly into alcohol, since the eosin is partially 

 an alcohol solution. At the end of five minutes the slide is taken out of 

 the alcohol, and, in order to be quite sure that there is no water still 

 clinging to the preparation, we incline the slide at a slight angle to the rag 

 with which we are holding it, and pour a few drops of alcohol from the 

 small bottle over it. If upon dropping oil of cloves on the preparation it 

 should be dark upon a dark sleeve or other dark background, we may 

 remove the oil of cloves with a few drops of xylol. Having quickly cleaned 

 the slide close up to the preparation, we place a drop of Canada balsam 

 upon it, which must be allowed to spread out before the cover-slip is 

 lowered upon it. 



Human blood is prepared in the same way, except that here the finger- 

 tip undergoes the surgical operation. 



Mitosis Staining.* — Dr. H. Zwaardemaker states that mitoses are most 

 successfully stained by the aid of a mordant. For hardening he usually 

 employs Flemming's chromo-osmium-acetic acid mixture, and then stains 

 the sections with an anilin-safranin solution. This is made by pouring 

 an alcoholic solution of safranin into about an equal volume of anilin water. 

 In this stain the sections remain from two minutes to an hour, the exact 

 length of time depending on the softness or the compactness of the tissue. 

 Decoloration is performed with slightly acidulated spirit. 



Colouring- the Nuclei of Living Cells.|— The most interesting fact 

 brought out in Mr. D. H. Campbell's work at Tubingen is the fact that 

 several anilin colours have the property of colouring the nucleus of many 

 plant cells without killing them. That the living nucleus can be stained 

 has been demonstrated by several observers in the case of animal cells, but 

 as far as he knows, it has not hitherto been observed in plant cells. Though 

 the work is not yet completed, he thinks it will be interesting to give briefly 

 some of the processes by which the results were obtained, and some of the 

 objects employed. 



The first colour used was dahlia, a violet-purple pigment, by whose aid 

 Lavalette had succeeded in colouring living spermatozoa and the nuclei of 

 sperm-cells. The most favourable object so far found by the author is the 

 nucleus of the cells of stamen hairs of Tradescantia. T. Virginica was 

 principally used, but other species gave equally good results. Hairs should 

 be chosen from young buds, as these are perfectly colourless, not having 

 developed the coloured cell-sap of the older hairs. The sepals and petals 

 are removed, and the stamens thus exposed are plunged into an aqueous 

 solution of the dahlia. After an immersion of from half an hour to three 

 or four hours, or even much longer, depending on the strength of the solu- 

 tion, it will be found that in many cases the nuclei are more or less deeply 

 coloured, and that the cell is not killed is evinced by the continuance of the 

 protoplasmic streaming. It is quite surprising to see how deep the nucleus 

 is often stained without killing the cell. A nucleus so coloured appears 



' Zeitschr. f. Wiss. Mikr., iv. (1887) p. 212. t Bot. Gazette, xii. (1887) pp. 192-3. 



