Ch. XI] PREPARATIONS BY THE COLLODION METHOD 391 



After haK an hour or longer the preparation is ready to stain. 



§ 635. The castor-xylene method of sectioning. — The prepara- 

 tion of the tissue is the same as described in § 625-629, except that 

 when the collodion is hardened in chloroform it is transferred, not to 

 alcohol, but the block is placed in castor-xylene (§ 554). In a few 

 days the collodion gets as transparent as glass and one can see the 

 tissue within with great clearness. It can remain in the castor- 

 xylene indefinitely. 



In cutting one proceeds exactly as in § 632, except that the block 

 is kept wet with castor-xylene and not with alcohol. The sections 

 are arranged on the knife and transferred to the sHde in the same way 

 as for alcohol sectioning (§ 633-634) . 



For fastening the sections to the slide, as no water is present, one 

 can add the ether alcohol at once. It is advantageous here to have 

 a mixture of ether two parts and absolute alcohol one part for melt- 

 ing the collodion in these oil sections. 



AUow the shde to remain in the air till the collodion begins to look 

 duU; then the slide may be transferred to a jar of xylene to remove 

 the oil. From the xylene it is transferred to 95 % alcohol and then 

 the shde is ready to be stained, etc., as described below (§ 638). 



§ 636. Steps in order for the collodion method. — 



Name 



No. 



Animal 



Date 



Fixer 



Time of fix 



Washed in water 



67 % ale 82% ale. 



Decalc. § 398 



67 % ale 82% ale. . 



In toto stain 



Washed in 



67% ale 82% ale.. 



95 % ale 



Ether-ale 



ii% eol 3% col.. 



6 % eol 8 % col. . 



Imbedded 



Chloroform 67 % ale. 



Or castor-xylene 



Sections cut fi's . . . . 



Stains 



Mounted in 



Remarks 



Double Imbedding in Collodion and PARAiriN 



§ 637. Need of double imbedding. — Some objects like ova with 

 considerable yolk and other objects in which the different parts are 

 of unequal density or very loosely bound together are advantageously 



