82 BACTERIOLOGY 



mate must be added, in order to prevent the growth of 

 micro -organism s. 



Imbedding in oelloidine, — The celloidine method is a very 

 convenient one. It consists in fastening the portions of 

 organs to bits of cork or wood by means of celloidine 

 dissolved in alcohol and ether, and then, after the celloidine 

 has set, immersing them in alcohol, in which they gain a 

 consistence suitable for cutting. The pieces are placed in 

 absolute alcohol and left there for twenty-four hours, after 

 which they are transferred to a mixture of equal parts of 

 alcohol and ether, and finally to a celloidine solution of 

 medium consistence, in which they remain for at least twenty- 

 four hours, in order that the tissue may become thoroughly 

 saturated with that substance. The pieces are now taken 

 out one by one and fixed to corks by means of celloidine, and 

 as soon as it has set in the air, which requires only a few 

 minutes, the pieces fastened to the corks are immersed in 

 very dilute (30 per cent.) alcohol. In this the celloidine 

 becomes cloudy after a short time, until after several days it 

 is changed into an opaque white mass of such firmness that 

 the piece of organ to be cut is securely adherent to its cork 

 support, and if this be now fixed in the clamp of the micro- 

 tome it is possible to obtain the finest sections. These 

 sections are enveloped, so to speak, in a mantle of celloidine, 

 which is capable of taking the aniline dyes. 



This method gives good results with Gram's process. 

 When it is wished to stain in this way several sections follow- 

 ing one another in series, the section stained- ^ in use at the 

 author's Institute is well adapted for this purpose. Several 

 sections having been laid in serial succession upon a 

 slide of larger size than usual, are covered with a nickel- 

 plated grating and clamped in the section stainer. The 

 whole is then passed through the various fluids and stains 



' Sold by Siebert in Vienna. 



