26 The method of section-cutting with improvements, 



handled so much. On the other hand the staining in toto has 

 two great drawbacks. Firstly, it very often happens that with 

 every care the colour does not penetrate to the centre of the 

 specimen, and even if this result has been attained it is very 

 difficult to stain the whole specimen in a uniform manner ; the 

 outer portions will generally be stained in a greater degree than 

 the inner ones. Secondly, it is necessary to keep the specimen in 

 the colouring solution for a long time to attain thorough staining, 

 and it is very difficult with most colouring liquids to prevent 

 maceration from spoiling the whole specimen. Even if the 

 specimen is kept on ice the epithelia will often be loosened and the 

 whole thing spoilt if the specimen is left in the staining solution 

 over night. 



In a hot country such as this it is difficult to prevent this. 



Any colour in solution will do for staining, and a wide scope is 

 left to the microscopist in this field. 



Aniline dyes have been extensively used of late, but although 

 they are of great help to those who study bacteria, they have not 

 yielded any good results with higher organisms. Eosin, Fuchsin, 

 Bismarckbrown, &c., have been tried. They stain very rapidly, 

 and diffuse through the tissue with greater rapidity than any 

 other colouring fluid. The fault they have is, that they stain 

 everything in the same way and nearly in the same degree, so 

 that one sees in a section stained with aniline dye hardly more 

 than in a section not stained at all. 



Carmine, in different solutions, is a very much better colour. 

 It stains the " chromatin " of the protoplasm very much, and all 

 the other parts of the tissue only faintly. We know in what 

 kind of cells and parts thereof this chromatin is contained, and 

 we can therefore attain a clearer insight into the structure of any 

 specimen by colouring with carmine, than we could with the 

 investigation of not coloured sections. The carmine can be 

 dissolved in various ways — I refer the reader to text-books on 

 Histology, mainly Renvier — the solutions I have found best are 

 those in alum and picric acid. Carmine powder is dissolved in a 

 concentrated solution of alum when still hot and immediately 



