1 64 PARAFFIN SECTIONING. [CH. VII. 



ing after the dehydration the slide is drained of alcohol and put down 

 flat and the clearer poured on, or the whole slide is immersed in a jar 

 of clearer (§ 303). Clearing usually is sufficient in a few minutes ; a 

 stay of an hour or even over night does not injure most sections. 



In mounting in balsam the clearer is drained away by standing the 

 slide nearly vertically on some blotting paper, or by using the waste 

 bowl and standing it up in the little funnel (Fig. 134). Then the bal- 

 sam is put on the sections or spread on the cover-glass and that placed 

 over the sections. 



For cataloging and labeling, see § 291-295. 



Fig. 137. Small spirit lamp modified into a balsam 

 bottle, or a glycerin or glycerin-jelly bottle, or a bottle 

 for homogeneous immersion liquid. For all of these 

 purposes it should contain a glass rod as shown in the 

 figure. By adding a small brush, it answers well for 

 a shellac bottle also. 



\ 



i 267. The Collodion Method with Alcohol. — A good method of procedure for 

 making collodion sections is to proceed exactly as described including \ 257, and 

 ; then instead of hardening the collodion in chloroform and clarifier, it is hardened 

 in 82% alcohol for a day or two before sectioning. In sectioning, the knife and 

 tissue are kept wet with 82% alcohol and the sections are dehydrated with 95% 

 alcohol and then fastened to the slide with ether alone or with ether-alcohol. 

 The staining and mounting (I 263-266) are as described. One may preserve the 

 tissue after imbedding for a long time in the 82% alcohol before sectioning, or for 

 successive sections. While this method appears somewhat simpler, the results are 

 not so satisfactory as by the oil-method given above. 



THE PARAFFIN METHOD. 



§ 268. As with the collodion method, the tissues are first properly 

 fixed and hardened and then entirely filled with the imbedding mass, 

 but unlike collodion the mass must be entirely removed before the sec- 

 tions are finally mounted. The tissue thus imbedded and infiltrated is 

 like a homogeneous mass and sections may be cut of extreme thinness. 



.§ 269. Harden perfectly fresh tissue in picric-alcohol (§ 315) 



