130 STAINING. 



number of minute particles which stain on the outside with methy- 

 len blue. In fixed cells, as is well known, these particles aggregate 

 together to form the " Nissl granules." MICHAELIS found similar 

 granules in liver cells. As the cells die, the stain leaves the granules 

 and passes into the nucleus. 



The behaviour of the living nucleus to methyl green has given 

 rise to some discussion. It appears that no uni-cellular organism 

 in which the nucleus was stained has been observed to move, 

 whereas the chlorophyll grains may take up the stain while the cell 

 is normally motile. No convincing case of staining of the living 

 nucleus has in fact been described. 



The question as to whether the cell elements which stain during 

 life are to be described as living or not is scarcely putting the problem 

 from the right point of view. If a dye obtains contact with the 

 interfaces between constituents of a cell, it will in all probability 

 be deposited there to a degree depending on the various properties 

 of the interface described previously. This may occur independently 

 of the fact as to whether one or both of the phases is living. 



Apart, however, from these questions, it must be conceded that these 

 so-called " vital stains " are frequently very useful. According to 

 BOLLES LEE'S experience, methylen blue is the most generally useful 

 of them. It has (with Bismarck brown, Congo red, and neutral red) 

 the valuable point that it is sufficiently soluble in saline solutions, and 

 may therefore be employed with marine organisms by simply adding it 

 to sea-water. The others are not thus soluble to a practical extent, 

 but BOLLES LEE finds that gentian and dahlia become so if a trace of 

 chloral hydrate 0-25 per cent, is ample enough be added to the saline 

 solution. Any of these reagents may be rubbed up with serum, or other 

 " indifferent " liquid. 



Methylen blue may be fixed in the tissues, and permanent preparations 

 made, by one or other of the methods described in Chap. XVI. 

 Bismarck brown stains may be fixed with 0-2 per cent, chromic acid or 

 with sublimate solution (MAYER), or 1 per cent, osmic acid (LoiSEL, 

 Journ. de VAnat. et de la PJiys., 1898, No. 2, p. 212 a work that contains 

 a good deal of information on the subject of intra-vitam stains), and the 

 preparations may be stained with safranin, care being taken not to 

 expose them too long to the action of alcohol. For the study of cell- 

 granules, neutral red is perhaps the best. 



FISCHEL (Unters. ueb. vitale Faerbungen, Leipzig, 1908) finds that 

 alizarin is specific for nerves. Add excess of alizarin to boiling water, 

 boil and filter, and add 1 vol. of the filtrate to the water containing the 

 organisms (Cladocera). The stain takes several hours. 



For sulphorhodamin, which is selective for many organs (kidney, 

 liver, uterus, skin, lymph-glands, etc.), see ANDREEW, in Virchow's 

 Arch., cciv, 1911, p. 447. 



The details of the various methods used for intra^ vital staining 



