A REVIEW OF THE GOLGI METHOD. 153 



injurious to the preservation of the microscopical sections. To 

 accomplish the latter the alcohol should be changed two or three 

 times till it remains transparent for a number of days after the 

 piece is brought into it. In this way the pieces can be kept a long 

 time. I have kept them for about nine years in this way, and can 

 obtain from them, when I wish, preparations as clear as those 

 obtained from them shortly after their preparation. 



" The further treatment of the microscopical sections corres- 

 ponds essentially with the usual procedure in obtaining anhydrous 

 preparations, except for some peculiarities necessary to overcome 

 some difficulties in the way of securing stable preparations. 



" The sections, before they are permanently brought into gum 

 damar or Canada balsam, must first be treated successively, 

 accordmg to the classical method, with absolute alcohol and some 

 clearing fluid. Each of these steps requires an especial care not 

 necessary with ordinary preparations. 



" {a) Treaimefit with absolute alcohol. The only rule to be 

 especially noticed here is that the sections must be very carefully 

 dehydrated by bringing them into three or four changes of pure 

 absolute alcohol. This is the only principal rule in order to obtain 

 a long preservation, for the more accurately and carefully the 

 dehydration is carried out, thereby freeing the tissue from the last 

 trace of silver nitrate, the more one can rely upon the preparations 

 remaining clear for a long time. 



" {b) Cleari?ig. The sections to be mounted must first be 

 brought, for clearing, from absolute alcohol into creosote, where 

 they remain some minutes, and then into turpentine. In the latter 

 they can remain a long while. The selection of these two sub- 

 stances, and their consecutive use, is another aid to securing a 

 long preservation. Among many other substances tried for clear- 

 ing I have also found oleum origani* for my method very useful, 

 but I have found no sufficient ground for abandoning the first 

 mentioned fluids. The sections usually remain in turpentine only 

 lo to 15 minutes, but may remain there longer.. 



" {c) Completion of the microscopical preparations. For perma- 

 nent preservation, the sections are brought from turpentine into 



* This oil, followed by washing in xylol instead of turpentine, is preferred 

 by the writer. 



