24 The Microscope. 



TECHNOLOGY. 



FINISHING BALSAM MOUNTS. 



WHEN the surplus balsam around the edges of the cover-glass 

 has become hard and brittle, the slides are ready for finish- 

 ing. The first step is the removal of this surplus, by scraping it 

 away with a pen-knife or other suitable instrument. Care must be 

 taken in doing this not to get the point of the blade under the 

 cover-glass, or in any way to distm-b the same; for while the exuded 

 resin may be dry and hard, that which is under the cover is pro- 

 bably still soft and fluid. For the same reason the operator must be 

 careful about making pressure on the cover-glass, as in this manner 

 a portion of the soft balsam may be forced out and its place taken, 

 too fi'equently, by an air bubble which is almost impossible to get 

 rid of. If such an accident should happen, it may sometimes be 

 remedied by placing a drop of balsam at the edge of the cover-glass 

 on the side opposite to the deficit. A needle is then inserted under 

 the cover-glass and the latter slightly raised. As it rises the added 

 balsam is drawn under it and a little manceuvering suffices to dis- 

 tribute the fluid evenly over the field. Before fresh balsam is added 

 in such a case, the slide in that neighborhood must be made as clean 

 as possible, since the balsam in entering will carry along with it any 

 particles of dust or dirt with which it may come in contact. After 

 refilling, the slide must be again laid away to recommence the pro- 

 cess of hardening. After scraping away as much of the dry balsam, 

 etc., as possible, place the slide on the turn-table and spin a ring of 

 arabicin or gelatin cement around the edge of the cover-glass. Let 

 dry, and as soon as this occurs, clean the slides thoroughly with a 

 linen rag moistened with benzol or turpentine. The ring of 

 arabicin prevents the cleansing fluid from invading the cell. After 

 the entire slide and the top of the cover-glass are cleaned, the ring 

 of arabicin cement may be rinsed off with clear water and the slide 

 labeled and put away. — Dr. F. L. James in St. Louis Med. and Surg. 

 Jour. 



A New Culture Medium. — Dr. Alex. Edington, assistant to the 

 Professor of Surgery at Edinburg University, says that a jelly de- 

 rived from Irish moss is much less opaque than agaragar and more 

 nutritious, and is thereftn-e to be recommended as a culture medium 

 for micro-organisms capable of withstanding high pressure. He 

 macerates 2 ozs. of the finest selected Irish moss in IS ozs. water, 



