June IS, 1915] 



SCIENCE 



911 



brightens (they are usually barely luminous), 

 while that on the other side becomes entirely 

 dark. For most physiological purposes a suffi- 



W^,g4'H'^ 



eient current is obtained if and C are 80- 

 watt carbon filament lamps and -D is a 50-watt 



or the signal magnet disconnected. With this 

 arrangement it is not easy for one careless stu- 

 dent to upset the entire system, and he is 

 easily located if he does. One lamp battery 

 operates effectively a large number of signal 

 magnets in series. 



When, as in work with the graphic method, 

 it is desired to have an automatic record on 

 the smoked paper of the instant at which some 

 nerve was stimulated, the arrangement shown 

 at the right in Fig. 4 is convenient. It con- 

 sists merely of another lamp battery, induction 

 coil and a double knife-edge switch. One blade 

 of the switch is connected as a making and 

 breaking key in the coil circuit, and the other 

 as a short-circuiting key in the time circuit. 

 Thus the interval of stimulation when the key 

 is closed is indicated on the graphic record by 

 the cessation of the movements of the signal 

 magnet, and the time record recommences the 



^^^^ 



lamp. For some physiological induction coils 

 (e. g., the Harvard coil) it is necessary, how- 

 ever, to use larger lamps (120 watts) in and 

 G'. If still more current is wanted two or 

 more sockets can be screwed to the board on 

 each side, connected in parallel and filled with 

 lamps until the needed current is obtained. 

 Fig. 3 shows the arrangement of the sockets 

 on the board. 



In Fig. 4 is shown a convenient method of 

 wiring the entire student laboratory for record- 

 ing time. The figure shows at the left the 

 lamp battery and the clock. The latter may 

 be placed either in series with the signal 

 magnets or so as to short-circuit the current, as 

 it is in the diagram. The signal magnets must 

 all be arranged on the line in series, each with 

 a short-circuiting key to be closed when the 

 time record at that place is to be discontinued 



instant the stimulation is ended by the re- 

 opening of the key. Tandell Henderson 

 Yale Medical School 



a simple device for demonstrating the 

 tempered scale 



The diatonic scale, consisting of a succes- 

 sion of eight tones and containing three inter- 

 vals known as " major second intervals," two 

 known as " minor second intervals " and two 

 " half-tones," is not adapted to musical instru- 

 ments of " fixed pitch " (e. g., the piano, harp, 

 etc.) for the reason that it does not without a 

 multiplicity of keys (strings) allow of trans- 

 position or change of keys. 



For fixed-pitch instruments, therefore, the 

 scale is modified in the following manner. 

 First, an additional tone is inserted in each of 

 the larger intervals (major and minor seconds) 



