17 



room and tlie physiological state of the animal, but an average 

 length oi' time was three days. The greatest clearness of impreg- 

 nation was secured with silver nitrate solution of 0.75^ strength. 

 In the preparation of serial sections, the most desirable clear- 

 ing agent was found in a mixture of oil bergamot, oil cedar- 

 wood, and melted carbolic acid crystals, equal parts. After 

 being hardened in chloroform, the celloidin blocks were placed 

 in the clearing mixture, and they were kept flooded with the 

 oil during cutting. The above mixture clears the block rapid- 

 ly, it may be used repeatedly, and it has the additional advan- 

 tage of allowing the preparations to be kept in it for some 

 time without impairing the impregnation. The sections were 

 cut 75 micra in thickness. 



2. The Application of Methylen-Blue . 

 Methylen-blue holds so many possibilities as a neurolog- 

 ical reagent that we are doubtless but crossing the threshold 

 of its use to day. I have applied this aniline in every way 

 of which I could learn, and the most important results are set 

 forth below. 



a. The Staining Method of Hissl. — Nissl's description of 

 his method ('94) called for the fixation of the tissues with 

 alcohol. This has proven an unsatisfactory part of the tech- 

 nique for my work. Better cytological preservation by far has 



