No. I.] DESMOGNATHUS FUSCA. 235 



For histological detail, the short silver nitrate method of 

 Golgi, andWeigert's hematoxylin method were mainly employed. 

 In the silver method the following proportions were used : 

 3% potassium bichromate 100 cc, 1% osmic acid 20 cc. The 

 tissue was allowed to remain in this mixture from twenty-four 

 to forty-eight hours, according to the temperature ; it was 

 then rinsed rapidly and placed in a weak solution (^ %) of 

 silver nitrate for fifteen or twenty minutes. This was changed 

 a couple of times until the fluid remained clear. It was then 

 immersed in a ^ % silver nitrate solution, and left there for 

 two days or longer. The addition of a drop of formic acid to 

 every 100 cc. of the silver solution, in order to facilitate reduc- 

 tion, as recommended by Van Gehuchten, was tried, but with 

 no apparent advantage or disadvantage. Single and double 

 impregnations of the silver were tried and very good effects 

 were obtained from each. It seemed as if the latter gave 

 more constant results. Collodion imbedding was employed 

 throughout. The object was cleared and cut in the castor- 

 thyme oil mixture : red oil of thyme, 3 parts, castor oil i part.^ 



If the specimen is stained in toto, the method is a very 

 expeditious one ; and it was found that the sections, after 

 absorbing the superfluous oil with tissue paper, could be fas- 

 tened to the slide by means of a drop or two of ether alcohol, 

 and that they might then be passed through the various alco- 

 hols and stained similarly to the paraffin or ordinary collodion 

 methods. Any tendency toward crumbling or tearing on the 

 part of the sections may be obviated by painting the cut 

 surface of the object with a thin layer of one per cent col- 

 lodion before making each cut. This will also enable one to 

 cut much thinner sections. 



Surface Anatomy. 



Macroscopic methods are of but little use, the average size 

 of the brain being about one and one half to two millimeters 

 in width and six to eight millimeters in length ; this in con- 



1 P. A. Fish. A New Clearer for Collodionized Objects. Proceedings of 

 the American Microscopical Society. XV, pp. 86-89. 1893. 



