APPENDIX. 471 



bility of the Eye to the Different Colours of the Spectrum' (Arch f. 

 OpUhalm., xvii, p. 123, 1871)." I would add that for lamp-light work, 

 especially fine work with high powers, either green or blue glass is, accord! 

 ing to my experience, a sine qud non if the best attainable results be 

 desired. I always use blue cover-glasses, putting from one to four of them 

 on the diaphragm of the condenser. For some unexplained reason I find I 

 get better results by means of several superposed thin glasses than by one 

 thick one. Spectral blue glass can be obtained from Mr. Pillischer, the 

 optician, in Bond Street. 



867. Object-holder to Cambridge Microtome. Since 271 

 was written the Cambridge Sci. Inst. Co. have brought out 

 an adjustable object-holder to their rocking microtome, fulfil- 

 ling the required conditions as regards facility of orientation. 



868. Obregia's Serial Section Method. This method, which 

 was originally described in the Neurologisches Centralb. for 

 1890, and is given in the third edition of WOODHEAD'S Prac- 

 tical Pathology, had escaped my attention. It has been lately 

 recommended for class purposes, as being very safe and con- 

 venient, by GULLAND (Journ. of Path., February, 1893). 

 Slides, or glass plates of any size, are coated with a solution 

 made of 



Syrupy solution of powdered candy- 

 sugar made with boiling distilled 

 water . . . . . v ; 30 c.c. 

 Absolute alcohol . . . 20 



Transparent syrupy solution of pure 



dextrin made with distilled water . 10 

 They are dried slowly for two or three days until the 

 surface is just sticky to the moist finger. Sections are 

 arranged and heated for a few minutes to a temperature 

 slightly above the melting-point of the paraffin. The paraffin 

 is removed by some solvent, such as xylol or naphtha, and 

 this is in turn removed by alcohol. The alcohol is poured 

 off, and the sections are covered with solution of celloidin or 

 with a solution of 3 per cent, of photoxylin in a mixture of 

 equal parts of ether and absolute alcohol. The plates are 

 left to evaporate in a horizontal position, and when the sec- 

 tions are required the sheet of collodion is cut into ribbons, 

 which are floated off in water, and further treated as desired, 

 e. g. as in Weigert's process, 340. (It is well to divide the 

 sheet of collodion into ribbons by running the point of a knife 



