GENERAL METHODS. 39 



phenol, or with equal parts of phenol and oil of bergamot, 

 or with oil of bergamot alone. The last two are especially 

 recommended. When objects are stained before imbedding,, 

 the whole block may be cleared before cutting.] 



B. ATTACHMENT WITH AGAR-AGAR. 



51. Agar-agar is recommended by Gravis (I) for the 

 attachment of microtome sections. A ^% aqueous solu- 

 tion of this substance is warmed for some time after the 

 mixture of the ingredients until quite homogeneous, then 

 filtered through a fine cloth or through glass wool, and finally 

 protected from spoiling by the addition of some pieces of 

 camphor. 



A drop of this solution is placed on the carefully cleaned 

 slide, the sections are laid upon this drop, and the whole is 

 warmed until the paraffine becomes soft without wholly 

 melting. Crumpled sections then spread out completely. 

 After the cooling of the slide the superfluous agar-agar is 

 taken up with filter-paper and the rest is allowed to dry com- 

 pletely. After this the paraffine may be removed by xylol, 

 as in the previous method, and the slide may be transferred 

 to alcohol. 



This method, which I have recently tried many times, 

 has the advantage that it admits of the use of rolled sec- 

 tions ; and even crumpling due to the imbedding may be 

 wholly or largely overcome. I have seen a troublesome 

 staining of the agar-agar only with haematoxylin. 



A disadvantage of the method, however, consists in the 

 fact that in pure water the solution of agar-agar, and there- 

 fore the separation of the sections, often occurs. But one 

 can always treat sections attached with agar-agar with solu- 

 tions in strong or 50$ alcohol, and can usually, with some 

 care, stain them with aqueous solutions. 



C. COMBINED AGAR-AGAR-COLLODION METHOD. 



The separation in water of sections attached with agar- 

 agar can be prevented by painting over sections attached by 



