172 THE AMERICAN MONTHLY [Jun 



ed out and one end corked, was connected with the glasi 

 tube by means of a wide rubber tube. The periosteum 

 was removed, and any holes visible on the outside were 

 plugged with wooden pegs. The tubing was then filled 

 the whole length with stain, to which a little antiseptic 

 had been added. The bone being in a dry room, dried, 

 and as this occurred the stain was drawn in to take the 

 place of the evaporated moisture. After about a month 

 all of the nuclei of the bone cells were found stained, and 

 also the lining membranes of the canals. The bone matrix 

 remained unstained, but the canaliculi were faintly out- 

 lined. 



New Lamp. — An electric microscope lamp has recently 

 been placed on the market by Messrs. J. Swift & Son. It 

 was designed by Mr. J. E. Barnard to give an evenly il- 

 luminated field in the microscope, without the image of 

 the filament of the incadescent lamp being thrown up from 

 the mirror in the field of view. This is efl"ected by a light 

 from the incandescent filament falling upon a flat plane 

 placed at an ang^le of 45° to the axis of the lamp, and the 

 surface of which is covered with a preparation which 

 throws off an intensely white light in such volume that 

 the largest mirror of any microicope can be fully illumi- 

 nated. The lamp is mounted on a swivel, enabling it to 

 be placed at any angle, and can also be lowered or raised 

 at will. 



Screen. — The focussing of a microscopic object on a 

 ground glass screen requires much skill and care. The 

 screen which is supplied with the ordinary camera is gen- 

 erally too coarse, and in high power photo-micrography 

 even the finest ground glass obtainable does not always 

 give satisfactory result*. For critical and medium work 

 it is essential that the focussing screen should be, as far 

 as possible, without grain. A simple way of preparing 

 such a screen is as follows : — Take an unexposed photo- 

 graphic dry plate and immerse it in a solution of chloride 



