FIXING AX1> MICROTOME SECTIONING 243 



into pieces as small as can be conveniently bandied. Tbese may 

 tben be prepared by the following processes: 



1. Fixing: If the material is to be used -imply for the study of 

 tissue -arrangement, cell-structure, etc., the treatment with alcohol 

 described in the paragraph relating to the preparing and keeping of 



laboratory material is sufficient preparation for the imbedding pr bs. 



Protoplasmic structures, however, are likely to be distorted or disin- 

 tegrated after this treatment, due to the slow process of killing. Some 

 method of quickly killing or "fixing "the protoplasm is therefore n< 

 sary. With hematoxylin Btaining only a few methods are available, 

 among which the following is perhaps t he besl . < !u1 the fresh material 

 into very small pieces (the smaller the and drop into BO-called 



absolute alcohol I '."> per cent <>r stronger) : after a few hours pres< i \ 

 in 90 or 95 per cenl alcohol. With other stains mere accurate fixing 

 agents may be used, such as chromic acid, osmic acid, acetic acid, 

 etc., either separately <>r in combination. The treatment, however, 

 is in these cases rather complicated. 



_'. Imbedding: The pieces musl be imbedded in some substance 

 in which they can be held and sectioned. For this purpose col- 

 lodion is generally used. Pour off the alcohol, and add enough - 

 cent collodion to cover the material about three-fourths of an 

 inch. After twenty-four hours this may be poured back into the 

 stock bottle, and an equal amounl of 5 per cent collodion put on the 



material. The i itains ether and alcohol, both of which 



:I|1 . volatile; therefore these operations musl be performed as quickly 

 as possible, and the corks of collodion bottles Bhould always be 

 sealed by holding the bottle neck down I w seconds. Ln 



the mate-rial in 5 per cenl collodion twenty-four hours, and then 

 pour the contents of the vial into a paper box, which may be made 

 l>v folding a piece of writing paper. T of the boi musl be 



judged bo that e.eh piece of material will be Burrounded I 

 quantity of collodion, and the inside of the box Bhould b< 



with vaseline t<> prevent th Ilodion from Bticking. Thi 



will sink t<> the I,, .item, where they ma) be arranged with a needle. 



If there is nol enough collodion in the box add some from I 



bottle. The box should then l>e placed in a -hallo . : on the 



bottom of which a little alcohol ha- been poured, at 



a pane of glass leaving > verj -mall opening on In about 



twenty-four hours the collodion will have hardened into 



ing the consistency of cheese. Tin- material may now t u1 Into 



small blocks and Btored in s "> per cenl alcohol. 



:;. < lotting: For outl sit her a hand mi< 



