The Microscope. 151 



second exposure. The amount to whicli the tilting takes place must 

 be only very slight else the apparent solidity of the image when 

 subsequently examined in the stereoscope will be exaggerated. 



Success in this is insured by employing an objective of small 

 angular aperture, or, should it be too wide, limiting this otherwise 

 excellent quality by a diaphragm cap being slipped over the end. 



Another way by which stereoscopic photo- micrographs can be 

 obtained by a monocular microscope is to employ an objective having 

 an effectively large front lense, and covering it with an easy-fitting 

 ■cap, having in it an aperture so much at one side as to cover up 

 one-half of the lense. When making the first exposure the cap is 

 turned so as to uncover one side of the lense and is rotated half a 

 turn before taking the second negative ; the resulting pair of pic- 

 tru-es will be stereoscopic. 



There are several other methods which may be employed and 

 which are more especially adapted for the higher powers. This 

 article is, however, mainly intended for the photo-microscopic aspir- 

 ant with limited appliances." — Scientific American. 



The Combined Use of Celloidin and Paraffin. — In the Zeit- 

 schrift fiir wissenschaftUche Mikroskopie, Kultschizky states that 

 the use of both celloidin and paraffin in imbedding microscopical 

 preparations has certain advantages over that of either material 

 alone ; the individual parts of delicate objects preserve their proper 

 relations; the preparation remains dry, and the process of making 

 sections does not require the use of alcohol, and sections can be 

 made as thin as when paraffin only is used. According to an 

 abstract contained in the Fortschritte der Medicin, the method is as 

 follows: The alcoholic preparation is allowed to lie for a few hours 

 in a mixture of equal volumes of alcohol and ether; it is then placed 

 for twenty-four hours in a solution of celloidin, the strength of which 

 is immaterial. It is now placed in ordinary oil of origanum, subse- 

 quently in a mixture of paraffin and oil of origanum, which should 

 not be over 104^ F. in temperature, and finally in melted paraffin. 

 The length of time that it should remain in the oil of origanum, in 

 the solution of paraffin, and in the melted paraffin depends on the 

 character of the object, and must be ascertained by trial. — New York 

 Medical Journal. 



