and Laboratory Methods. 1616 



small pins at either end and the lateral nerves are laid out in their normal posi- 

 tions. The salt solution is then poured off, leaving the pieces of cord straight 

 and rtat against the bottom of the pan. A considerable quantity of vom Rath's 

 fluid (formula given above) is now poured into the pan and the tissue is left in 

 this for two hours for thorough fixation. In a short time (fifteen to twenty min- 

 utes) after this fixation has begun the pins may be removed, and the pieces of 

 cord handled freely without danger of distortion. After removal from the fixing 

 fluid the tissue is washed in methyl alcohol ; blackened in pyroligneous acid 

 from eight to twelve hours, and washed again in methyl alcohol. The pieces 

 may now be dehydrated in 96 per cent, and absolute alcohol, cleared in cedar oil 

 and embedded in paraffin. 



Pieces of the cord from three-fourths to one and one-half centimeters long 

 prepared in the way described are cut into longitudinal sections twenty mikrons 

 thick. The plane of cutting is made as nearly as possible horizontal, i. e., at 

 right angles to the median dorso-ventral plane of the cord. The sections are 

 then stained on the slide by the Heidenhain ironhcEmotoxylin method and then 

 differentiated in a two per cent, iron alum solution till the axis cylinder processes 

 alone retain the color. The sections are faintly counterstained with orange G 

 and, after dehydration and clearing, mounted in balsam. 



The resulting preparations show the nerve fibers stained an intense black on 

 a light yellow field, and as a result of the great thickness and the plane of cut- 

 ting of the sections, a single fiber may be followed along the cord for a long 

 distance. For precision and distinctness in the differentiation of fiber elements 

 these preparations leave little to be desired, and the simplicity of the process as 

 compared with other nerve methods is a decided recommendation. 



Zoological Laboratory, University of Michigan. RAYMOND Pearl. 



A Convenient Case for Butterflies and Moths. 



Many enthusiastic collectors of butterflies and moths have been discouraged 

 by having their specimens destroyed by museum pests. 



In order that a collection may be of greatest value it must be so arranged 

 that the specimens may be readily examined and at the same time so arranged 

 that they may be permanently preserved. Many attempts have been made to 

 accomplish this. 



The Harvard cabinet fulfills the first requirement, but it is not wholly satis- 

 factory as regards the second. Furthermore, in examining the specimens they 

 are sooner or later badly damaged. Especially is this the case when the speci- 

 mens are used in class work. 



The Denton Brothers' Butterfly Tablets come more nearly meeting the 

 requirements. In this case the specimen is sealed up between a plaster cast 

 and a plate of glass. This makes a compact case and readily handled without 

 danger to the specimen. A very serious objection, however, is to be raised to 

 this method of preserving, which is that only one side of the specimen can be 



