and Laboratory Methods. 



1369 



It would have been an advantage to have had one of the rods marked off in 

 quarter inches, so that once the length of bellows for a certain enlargement had 

 been accurately measured, the back of the camera could at any time be brought 

 to the same position without any delay in measuring. This point was overlooked, 

 but I have had (]uarter-inch spaces marked in white paint on the flat surface of 

 the upper connecting iron casting, and this answers the purpose just as well. 

 (See plan of room, Fig. 2.) 



The optical bench carrying lamp, microscope, and accessories is 4 feet by 

 15 inches and is a turntable, revolving upon the supporting column, so that it 

 can be turned partially round ; the operator sitting on a low stool to find the field 

 and rough focus. 



Since the dark room is on the left of the apparatus, looking towards the 

 source of illumination, the table has been constructed to turn to the left, and 

 everything else is so arranged that it can be manipulated from the left, thus 

 obviating any necessity for walking around the apparatus. ^ 



The accompanying diagram illustrates the plan of the room, 11 xl5 feet, the 

 dotted lines showing the optical bench in position for finding the field. Of the 

 camera stand only the steel rods on which the camera runs, and the central beam 

 with some of the markings, are indicated. The lamp and accessories run on steel 

 rods, which are supported on a wooden table, supported in its turn on leveling 

 screws, which run in a metal groove on the surface of the optical bench, so that 

 the table can be moved backward or forward as required. 



Fig. 3 — Epithelioma invading lympli node, x 70. Lens, Powell & 



Leland i in. apochromatic ; ocular, none; exposure, '^ 



sec. ; distance of plate from hood, 70 inches. 



The rheostat is a Colt adjustable, and stands on the floor just below the 



illuminating end of the optical bench. I had previously used an automatic arc 



