THE CELLOIDIN METHOD 133 



was recommended by Merkel and Schiefferdeckei-i in 1882. The princi- 

 pal features of the method are as follows : Material is dehydrated in 

 absolute alcohol, treated with ether-alcohol, infiltrated with celloidin, 

 imbedded in celloidin, hardened in chloroform or alcohol; after which, 

 it is cut, stained, and mounted. 



Eycleshymer, who brought the celloidin method to a high degree 

 of efficiency, pubhshed in 1892 a short account, which may be sum- 

 marized as follows: Put the celloidin tablet, or fragments, into a wide- 

 mouthed bottle, and pour on enough ether-alcohol (equal parts ether 

 and absolute alcohol) to cover the celloidin. Occasionally shake and 

 add a little more ether-alcohol until the celloidin is all dissolved. The 

 process may require several days. The solution should have the con- 

 sistency of a very thick oil. Label this solution Number 4. Solution 

 Number 3 is made by mixing 2 parts of solution Number 4 with 1 part 

 of ether-alcohol. Solution Number 2 is made by mixing 2 parts of 

 Number 3 with 1 part of ether-alcohol. Solution Number 1 consists of 

 equal parts of ether and absolute alcohol. 



After dehydrating, the material is placed successively in solutions 

 1, 2, 3, and 4. For an object 2 mm. square, 24 hours in each solution is 

 sufficient; for the brain of a cat, a week is not too long. 



A paper tray may be used for imbedding. Pour the object, with the 

 thick solution, into the tray and harden in chloroform for 24 hours; 

 then cut away the paper and place the block in 70 per cent alcohol for 

 a few hours. The material may be left indefinitely in a mixture of 

 equal parts of 95 per cent alcohol and glycerin. 



Before cutting, the object is mounted upon a block of wood. A 

 block, suited to the microtome clamp, is dipped in ether-alcohol, which 

 removes the air and insures a firmer mounting. Dip the end of the 

 block of wood in solution Number 3, and the piece of celloidin contain- 

 ing the object in solution Number 1. Press the two firmly together, 

 and place in chloroform until the joint becomes hardened. 



Set the blade of the microtome knife as obliquely as possible. Both 

 the object and the knife should be kept flooded with 70 per cent alco- 

 hol, and the sections, as they are cut, should be transferred to 70 per 

 cent alcohol. 



Stain in Delafield's haematoxylin for 5-30 minutes. Wash in water 

 for about 5 minutes, and then decolorize in acid alcohol (2-5 drops of 

 hydrochloric acid to 100 c.c. of 70 per cent alcohol) until the stain is 



1 Merkel and Schiefferdecker, Archiv fur Anatomie und Physiologie, 1882. 



