326 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



shows the object or the subject to the photographer on a ground 

 glass placed in focus. 



The apparatus is run by an electric motor of 0.7 horsepower sealed 

 directly into the concrete masonry. Normally it gives 1,500 revolu- 

 tions per minute, but this speed can be reduced one-half by means of 

 a rheostat. 



The movement of the motor is transmitted by a belt to a horizontal 

 intermediate shaft supporting several pulleys. By means of this and 

 another belt, the rotation is communicated to another horizontal 

 shaft either directly or by means of speed reducers. This shaft 

 operates the camera apparatus and shutter; the operation is thus 

 maintained perfectly synchronous with that of the moving-picture 

 apparatus. The speed reducers are fixed very conveniently on the 

 slot of the steel table; they can be clamped one following the other 

 so that the first one receiving the movement by a belt of the inter- 

 mediate shaft transmits it, reduced in speed to a second reducer, 

 then if necessary to a third. Each reducer is characterized by its 

 coefficient of reduction and on combining these coefficients, the varied 

 speeds can be obtained. 



The shutter rf is a balanced sector that cuts the light ray as near 

 as possible to the microscope. In tliis manner, the microscopic 

 preparation is neither hghted nor heated during the time of closing, 

 thus taking care of the delicate micro-organisms. 



The microscope can be enclosed in an electrically heated chamber 

 n, and in this way the preparation can be maintained at a constant 

 favorable temperature just as in a bacteriological chamber. The 

 front side of this chamber is of glass wliich permits passage of fight 

 rays. The ocular emerges from the upper part of the chamber, and 

 at a convenient place on the side are knobs for regulating the focus 

 and the movements of the mirror (pi. 2). 



To prevent a loss of several meters of film, since the apparatus 

 when started requires a certain time for stopping when the electric 

 current is cut. Dr. Comandon has added a brake to the shaft of the 

 motor. 



Finally, a special operating part, invented by Dr. Comandon and 

 De Fonbrime, controlled by a chronometer, permits setting the 

 apparatus automaticaUy into movement, stopping it, and starting it 

 up again at the end of a desired time. In this fashion the photo- 

 graphs can be made automaticaUy at any moment fixed in advance 

 by the operator and also during his absence. The time recorded on 

 each image (in the upper corner of the film) shows the exact time at 

 which any modification or movement registered on the film is produced. 



Another problem, not less complicated, consists of guarding in 

 good condition the life of the organisms and cells that are being 

 photographed. Two accessory parts can be utilized for this purpose: 



