PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS. 205 



being withdrawn in the same manner when the desired effect has been 

 produced, and being replaced by the preservative medium. For taking- 

 up sections without injury to them, and transferring them from one ves- 

 sel to another, recourse may be advantageously had to the ' lifter ' of Dr. 

 Sylvester Marsh ' (Fig. 137); which is a strip of German silver or copper 

 of the thickness of stout cardboard, 7 inches 

 long and 5-8ths inches broad, each end of 

 which, carefully smoothed and rounded, is to 

 be turn sd at the distance of 5-8ths inch to an 

 angle of about 35 . One end is to be left plain, 

 for lifting the section with some of its fluid, 

 when it is to be deposited on a slide; while 

 the other is perforated for letting the fluid 

 escape, when the section is to be floated-off 

 into a vessel filled with some different fluid. 



202. The relative value of different Stain- 

 ing Agents, the best modes of applying them, 

 and the benefits derivable from their use in 

 the study of the minute structure of Man and 

 the higher Animals, 2 have now been pretty 



fully determined by Histologists; and consid- ' "^Marsh's Section-ufter. 

 erable progress has also been made in the ap- 

 plication of the differential straining process to the various parts of the 

 higher Vegetable fabrics. 8 But there is still a wide field which has been 

 as yet but little cultivated, in the application of the staining process to 

 the study of the lower Organisms of both Kingdoms; and every one who 

 is engaged in the minute investigations of any particular group, musb 

 work out for himself the modifications which the ordinary methods may 

 require. All that can be here attempted is to give such directions as to 

 the agents to be employed, and the best modes of using them, as are likely 

 to be most generally useful. 



a. Carmine. This was one of the first Dyes employed for staining purposes ; 

 and its value was specially insisted on by Dr. Beale, as enabling living Pro- 

 toplasm (by him designated ' germinal matter,' or ' bioplasm') to be distinguished 

 from any kind of ' formed material.' It has a special affinity for cell-nuclei (pro- 

 toplasts) and the axial cylinders of white nerve-fibres; and thus, if the substance 

 to be stained be only left in the carmine fluid long enough for it to dye these 

 substances, they are strikingly differentiated from all others. It is essential that 

 the fluid should have a slight alkaline reaction, especially where the substance 

 has been hardened with chromic acid. The presence of too much alkali is inju- 

 rious; the want of it, on the other hand, causes the dye to act on the tissues 

 generally, and thus negatives its differentiating effect. Dr. Beale directs it to be 

 prepared as follows: Ten grains of Carmine in small fragments are to be placed 

 in a test-tube, and half a drachm of strong Liquor Ammonise added ; by agitation 

 and the heat of a spirit-lamp the carmine is soon dissolved, and the liquid, after 

 boiling for a few seconds, is to be allowed to cool. After the lapse of an hour, 

 much of the excess of ammonia will have escaped; and the solution is then to be 

 mixed with 2 oz. of Distilled Water, 2 oz. of pure Glycerine, and oz. of Alcohol. 

 The whole may be passed through a filter, or, after being allowed to stand for 



1 See his useful little Treatise on "Section-Cutting." 



2 See the "Treatises on Practical Histology" by Prof. Rutherford, Prof. 

 Schafer, Dr. Heneage Gibbes, Prof. Ranvier, Prof. Frey, and others; " How to 

 Work with the Microscope " by Dr. Beale; and Davies's " Preparation and Mount- 

 ing of Microscopic Objects " (2d Edition, edited by Dr. Matthews). 



3 This has been chiefly carried out in the United States by Dr. Beatty, Mr. 

 Walmsley, and Mr. Merriman, whose processes are described in the successive 

 volumes of the "American Journal of Microscopy." 



