306 APPENDIX 



Rapid method (Gilson). The dehydrated tissue is placed in 

 ether for an hour or more, then in thin celloidin in a short test- 

 tube, and this is placed on a bath in melted paraffin until the 

 solution is reduced to about Srds in bulk. 



It is then poured into a watch-glass placed with some of 

 the thickened celloidin on a small block of hardened celloidin ; 

 after a few minutes the block is placed in a mixture of equal 

 parts of chloroform and cedar-wood oil for an hour or more, 

 fixed to a block and cut, moistening the razor and the tissue 

 with cedar-wood oil. Lee recommends gradually increasing the 

 amount of cedar-wood oil and cutting without moistening the 

 razor. 



Cutting in celloidin with the freezing microtome. The celloidin 

 around the specimen is pared away, and the block placed in 

 water for an hour or two, then transferred to gum for any 

 longer time. 



Or, though less satisfactorily, the block after soaking in 

 water may be simply dipped in gum to make it stick to the 

 microtome. 



The sections are placed in water to remove the gum ; this is 

 done more quickly if warm water is used. 



If it is desired not to soak the tissue with water, the block may 

 be passed through 95 p.c. alcohol (1 day); xylol (1 to 2 hrs.), and 

 anethol (melting point 20 C., 6 to 8 hrs.); the cooled block can 

 then be frozen and cut. 



Celloidin and paraffin, (a) The tissue is soaked in thin 

 celloidin for 1 to 3 days and hardened. The block is placed for 

 an hour in origanum oil, then in origanum oil and paraffin at 

 about 38 C. for several hours, and finally in melted paraffin 

 (of melting point about 50 C.) for two or more hours. 



(6) The tissue is soaked in a mixture of 4 parts of 2 to 

 3 p.c. celloidin solution and 1 part cedar-wood oil ; hardened in 

 a mixture of 4 parts chloroform and 1 part cedar- wood oil ; put 

 in xylol at 30 C., to which paraffin is added to saturation. Then 

 in paraffin at 50 C., which is changed once or twice. 



In these cases it is not necessary to moisten the razor, and 

 if a paraffin mantel is left serial sections can be cut. 



