PRELIMINARY TREATMENT 215 



of metal are pushed apart and the paraffin with the tissue embedded is 

 free. 



B. Toluene method. The technique is exactly the same as when using 

 xylol except that toluene is substituted for xylol. 



C. Ether method. 1. When the tissue is taken out of absolute alcohol it 

 is transferred to alcohol-ether for from 30 minutes to 6 hours according to 

 the size of the tissue. 



2. The tissue is then immersed in pure ether for at least as long as it was 

 in the alcohol-ether mixture. 



3. It is then transferred to an hermetically sealed flask containing ether 

 saturated with paraffin melting at 50 C. and placed in the warm incubator 

 at 37-38 C. (see under xylol for duration of treatment). 



4. The block is now immersed in paraffin melting at 50 C. and embedded 

 in the manner described under xylol. 



4. Preliminary treatment of sections. 



Before sections can be stained the paraffin which has penetrated the 

 interstices of the tissue must be removed. 



A. Method recommended. 1. As soon as they are cut the -sections are 

 placed in a ground-glass stoppered vessel containing ether which rapidly 

 dissolves the paraffin. The length of time required will vary 



from several minutes to a few hours according to the size and 

 number of the sections treated. 



2. When all the paraffin has dissolved the sections are trans- 

 ferred with a platinum or nickel spatula (fig. 158) to a second 

 bath containing absolute alcohol. 



3. After being in absolute alcohol for a few minutes the sections 

 are transferred one by one with a spatula to a glass dish full of 

 distilled water. As soon as they come in contact with the water 

 the sections spin round and round very rapidly and at the same 

 time unroll and spread themselves flat. 



If the sections are very thin and fragile this gyratory movement 

 may tear them and render them useless, so that it is better to pass 

 such sections from absolute alcohol to 70 per cent, then to 40 per cent, 

 alcohol before placing them in distilled water. 



4. To transfer a section to a slide, dip the slide obliquely into 

 the water and beneath one of the sections, then fixing the section 

 with a needle raise the slide and gently draw it out of the water, 

 holding the section with the needle about the centre of the slide 

 on which it will spread out. Blot up the excess of water with a 

 cigarette paper or a piece of silk paper (which should be kept 

 ready cut up into small rectangular pieces, and not torn off as 

 required since the rough edges might pick up the section from 



the slide) and the section is now ready for staining. FlG . 158 _ 



_ Section lifter. 



B. Albumin fixation. The method just described is the simplest 



and, in the hands of those used to the work, applicable to the majority' of 

 cases. But when the sections are very delicate sections of lung, for instance, 

 there is a risk that they may be torn during the various manipulations. 

 In such a case it is invariably necessary to fix the section on the slide 

 immediately it is cut. The fixative generally used in bacteriology is Mayer's 

 albumin. 

 Mayer's albumin. Beat up the white of two eggs into a snow, leave them 



