PRESERVATION OF SPECIMENS 133 



After being taken from the formalin solution the specimens are 

 placed in methylated spirit for ten minutes, and then in a fresh 

 bath of methylated ; in this the colour to a large extent returns, 

 and they should be carefully watched and not allowed to remain 

 in it for more than an hour. They are then mounted in the 

 following mixture : 



Glycerine 400 c.c. 



Potassium acetate ..... 200 grm. 



Water 2,000 c.c. 



A trace of formalin should be added to this. 



Dele/pine describes an ' ; arsenious acid jelly " method for pre- 

 serving pathological specimens (Journ. Pathol. and fiacter., vol. 

 xviii, 1914, p. 345), 



The writer has preserved meat infected with 7v prodigiosns 

 very satisfactorily by the following method. Slices were cut off 

 and placed in the formalin solution given above for a few hours. 

 They were then well drained and placed in suitable glass capsules. 

 Ordinary nutrient gelatin was melted and sufficient poured in to 

 cover the specimens, and when it had set a little formalin was 

 poured on and allowed to remain for a few days. It was then 

 poured off and the glass top cemented down. 



For further information on preparation of tissues, section 

 cutting, staining methods, etc., see The Microtomisfs Vade 

 Mecnm, Bolles-Lee Practical Histology, Schrifer : Methods of 

 Morbid Histology and Clinical Pathology, Walker Hall and Herx- 

 heimer ; and Lehrbuck der MikrosJcopischen Tcchnllc, Rawitz. 



ADDENDUM. 



With regard to the mechanism of Gram staining (p. 118), 

 Beriians holds that the retention of the dye compound is depen- 

 dent upon the structure and integrity of the cell-membrane and 

 not upon chemical fixation of the dye compound by the bacterial 

 protoplasm. 



