The Microscope. 287 



MOUNTED ON GLASS. 



Daylight. 



Concave mirror, y\j in xffs.ffus + 



Plane mirror, ^^\n Tn-i.l^a + 



Lamplight. 



Concave mirror, ^^j, in 



Plane mirror, ^^^ in T^-s.hs 



111. through objective, -^ijin. xijff!otTTT 



A number of comparisons were made at each position and in 

 the same temperature. 



A Spencer objective was used for these measurements. But 

 Bausch & Lomb and Gvindlach objectives were also tried, obtaining 

 the same results. 



The microscope used is one constructed on my late patents, 

 and has a micrometer for measuring similar to a cob- web micro- 

 meter. But instead of cob- webs, three movable steel pointers are 

 used which are worked as fine as this metal will permit. The stage 

 is mechanical, and the main slide is moved with great precision by 

 a fine screw, 100 threads per inch. 



Subscriber: There are two grades of paraffin used in embryo- 

 logical and other microscopical work, for embedding. In winter the 

 hard grade is rather too hai'd, and requires to be softened with the 

 paraffin having a lower melting point, say in the proportions of 1 to 

 3. It is important, too, in making serial sections, that the block, or 

 at least the paraffin around the embryo, shall be soft enough so that 

 the edges of the sections will adhere. For making very thin sections 

 of animal tissues, the hardest paraffin is the best. 



As A result of the microscopical examination of a tooth implanted 

 by Younger's method, Curtis concludes that the inflammation conse- 

 quent to the formation of the new socket produces an infiltration of 

 osteoblasts into the cementum of the implanted tooth, which results 

 in bony anchylosis, thus fixing the tooth firmly in place. He 

 believes that not only the cementum recovers its life, but also the 

 dentine of the root, his sections showing that the dentine fibres were 

 not shrunken, and that the peripheral cells of the pulp, the odonto- 

 blasts, were alive. — Boston Medical and Surgical Journal. 



Dr. Sternberg has been studying the liquefaction of gelatine 

 by bacteria, and has ascertained that it is due to a soluble chemical 

 product which is formed during the active growth of the liquefying 

 organisms, and that a comparatively small amount of this substance 

 will liquefy gelatine quite independently of the living organism. 

 Dr. Sternberg expresses the hope that some chemist will take up the 

 question with a view to ascertaining the exact nature of this sub- 

 stance. —Science. 



