3S6 PREPARATIONS BY THE PARAFFIN METHOD [Ch. XI 



When the paraffin is removed the staining and other operations 

 necessary for a completed preparation may be undertaken (see for 

 these § 639). 



§ 622. Collodionizing the sections. — Except for carmine stains and 

 perhaps some others, collodion remains practically colorless. While 

 the sections remain quite firmly attached to the slide after they have 

 been spread and dried, thick sections are liable to come off in the many 

 processes of staining, and if one has many sections on a slide some 

 of them may become loosened. To avoid this, the sections are covered 

 with a delicate layer of collodion, which holds them down to the slide. 

 The early method was to use a soft brush and paint a thin film over 

 the dried sections before they were deparaffined. Now the sections 

 are deparaffined, and then, after draining the xylene from the slide, 

 10-15 seconds, it is put into a bottle containing § % collodion (§ 556). 

 In a minute or more the collodion displaces the xylene and penetrates 

 the sections and forms a delicate veil over their free surface. No harm 

 is done by leaving the sections in the collodion a considerable time, 

 but a minute or two is sufficient. The slide is removed, allowed to 

 drain for half a minute, and then put into a jar of 67 % alcohol 

 (fig. 232). The alcohol fixes the collodion and removes the ether. 

 As the 67 % alcohol does not hurt the tissue, it may stay in the jar a 

 day or more, if desired, but half an hour suffices. 



The sections are now ready for the subsequent staining and other 

 operations to make a finished slide. One has to remember that if 

 mucicarmine (§ 549) is to be used in staining, the preparation must 

 not be collodionized, as carmine stains collodion. 



§623. Steps in order for the paraffin method. — ■ 



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