BY R. VON LENDENFELD, PH.D. 27 



filtered ; a deep red solution passes through and can be used as it 

 is, or for very tender specimens diluted with 50 % of destilled 

 water. This alum-carmine stains the nuclei of all cells ; the ova 

 spermatozoa and ganglia cells, and also muscular and gland cells very 

 intensely, whilst it gives to the oi'dinaiy connective tissue only a 

 slight red tinge. 



Picric-acid-carmine is a most excellent colouring fluid for the 

 tissue of higher animals. It stains like the foregoing, the nuclei, 

 ganglea cells, &c., red, but the picric acid in it at the same time 

 colours the horny substance of the skin and also nerve fibres 

 intensely orange-yellow. 



Hfemotoxylin is also an excellent staining fluid, prepared 

 according to the Kleinenberg. It stains the oixlinary protoplasm 

 light violet and the nuclei dai-k violet, nearly black. 



I refer the reader who may wish to collect some further particulars 

 on this subject to the standard works on Histology by Renvier 

 and Klein. 



Preparation. 



After the specimen is coloured it must be well-washed so as to 

 remove all colouring matter, which has not entered the protoplasm 

 or other parts of the specimen in a fixed combination. 



Cold water will in most cases be the best thing. For Haema- 

 toxylin, spirits. 



When the specimen is svashed it can either be imbedded in gum 

 Glycerine, frozen and cut forthwith or imbedded in gum glycerine 

 enclosed in liver, hardened in spirits and cut with the hand as 

 described above, or also prepared for imbedding in paraffin. 



I, together with many other zoologists, consider the paraffin 

 imbedding method to be far superior to any other. 



The first thing to be done with the washed specimen to prepare 

 it for imbedding in parafiin, is to extract all the water from it by 

 means of alcohol. This is a very difficult operation in the case of 

 veiy tender specimens, and requires gi'eat patience and care. 



If the specimen is placed in strong spirits immediately it will 

 shrink and become totally useless, because the water is extracted 

 from it by the strong hygroscopic spirits with such great violence. 



