CHAPTEK VII 

 THE CELLOIDIN METHOD 



Use the tissues which were prepared for this method including 

 pieces of the brain and spinal cord which were fixed in Erlicki's 

 fluid. Reserve a piece of spleen for the freezing method, 

 chap. viii. 



1. Fixing, washing, and dehydrating are the same as usual 

 (chap, iii) . If the object is in 70 per cent, alcohol, complete the 

 dehydration by using successively 95 per cent, and absolute alco- 

 hol. It should remain in the absolute alcohol for from 12 to 24 

 hours. 



2. From absolute alcohol transfer the object to equal parts of 

 absolute alcohol and ether 12 to 24 hours. 



3. Next, to thin celloidin for from 36 hours to several days. 



4. Thence to thick celloidin for from 24 hours to several days. 



5. Prepare a wooden block in such a manner that it will have 

 surface enough to accommodate the object, leaving a small margin, 

 and length enough to be readily clamped into the carrier on the 

 microtome (Fig. 32). Dip the end of the block to which the 

 object is to be attached into ether-alcohol for a minute and then 

 into thick celloidin. Let it dry so that later air bubbles will not 

 work up out of the wood into the imbedding mass. 



6. Oil one side of a strip of stiff paper by rubbing on a very 

 little vaselin, and wrap it, oiled surface in, about the prepared 

 end of the block in such a way that it will project beyond the 

 end of the block, forming a collar high enough to extend a little 

 beyond the object which is to be placed within it. Tie the paper 

 in place by means of a thread. 



7. Pour a small amount of thick celloidin into the paper cup 

 thus formed and with forceps remove the piece of tissue and place 

 it in celloidin. Add more thick celloidin until the cup is full. 

 By means of needles which have been moistened in ether-alcohol 

 arrange the object so that it will be cut in the desired plane. 



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