2292 



Journal of Applied Microscopy 



GENERAL PHYSIOLOGY. 



RAYMOND PEARL, University of Michigan. 



Books and Papers for Review should be Sent to Raymond Pearl, Zoological Laboratory, 

 University of Michigan, Ann Arbor, Mich. 



Porter, W. T. New Inductorium, Kymograph, Dr. Porter describes in this paper im- 



Heart Lever, Heavy Muscle Lever, and , r r i r .1 • 



Square Rheochord. Proc. Amer. Physiol. P^'Oved forms of several of the import- 



Soc. Fifteenth Ann. Meeting. Amer. Jour. ant pieces of physiological apparatus 



Physiol. 8: pp. xxxv-xli, 1903. 



which he has designed. An improved 



inductorium is shown in Fig. 1. The primary coil is fastened to the hard rubber 

 head piece, which bears on its outer face the antomatic interrupter and binding 

 posts. All the connections of the primary coil and interrupter are made on the 

 face of the head piece in plain view, there being no concealed wires. The 

 secondary coil slides on brass rods fastened to the head piece. Each end of the 

 secondary wire is fastened to a brass bar screwed to the ends of the hard spool. 

 The brass bars bear a trunnion which revolves in a split brass block, the fric- 



FiG. L 



tion of which is regulated by a screw. The trunnion block is cast in one piece 

 with a tube 3 cm. in length, which slides upon the slide rods. The secondary 

 spool revolves between the side rods in a vertical plane. When the secondary 

 coil has revolved through 90°, a pin upon the side bar of the secondary coil 

 strikes against the trunnion block and prevents further movement in that direc- 

 tion. The right hand side bar bears a half circle graduated upon one side from 

 0° to 90°. An index pointer is fastened upon the trunnion block. One side 

 rod is graduated in centimeters. This arrangement for the movement of the 

 secondary coil makes the inductorium as a whole very compact. The side rods 

 end in the secondary binding posts, so that moving the secondary coil does not 

 drag the electrodes. Next the binding posts is placed a substantial " knife 

 switch " short circuiting key, with hard rubber handle. 



The most noteworthy single feature about the improved kymograph is the 

 drum. The drum is made of aluminium, cast in one piece, turned true in the 



