1895 THE MICROSCOPE. 191 



It does not harden tissues nor make them stiff. For this 

 reason insects can be preserved indefinitely in carbolic acid in 

 a fit condition to be mounted at any time. The more delicate 

 parts are rendered quite transparent by long soaking in the sol- 

 ution, but this is no detriment to them. 



Carbolic acid is not an acid but belongs the chemical series of 

 alcohols. 



Insects are killed instantly by immersion in the acid and when 

 thus killed their parts will generally be found to be spread out. 



The carbolic acid used should be the strongest solution. 



Obtain the crystals and dissolve them in just water enough 

 to keep it fluid at ordinary temperatures. To use it for mount- 

 ing it is only necessary to drop the specimen iuto the acid and 

 in a few moments transfer it to the medium in which it is to be 

 mounted. 



India Rubber for Glycerine Mounts. — The following is 

 said to act satisfactorily for glycerine mounts. Heat India- 

 rubber till it becc'Qies sticky ; dissolve it in benzol, ring both 

 cover and slide, then let it remain till tacky ; arrange the object 

 in glycerine., press down the cover, wash away spare glycerine 

 and use asphalt varnish or other finish. 



SCIENCE-GOSSIP. 



Library Catalogues as a Possible Means of Infection. 



— The Independent says : " It is remarkable that in this day of 

 germs and germicides nobody has invented a sanitary library 

 card catalogue. Every one that recalls the unspeakable filth of 

 the old and now departed card catalogue of the Astor Library 

 must suspect that it was a highly -effective agency in the spread- 

 ing of disease. The bound catalogue is perhaps even worse, for 

 an attentive observer must often have noted that the average 

 reader in a j^ublic library turns the leaves of the catalogue with 

 the aid of a finger dampened by application to his own lips. 

 The commercial exchange of germs by this method must reach 

 a vast volume of transactions in the course of a year." 



