September 5, 1913] 



SCIENCE 



335 



direct from the dry cell and wound around tte 

 rod or arm supporting the top of the drum, 

 bent so that the short, bare, free end is 

 directed downward. Now a second copper 

 wire may be led from the opposite pole of the 

 cell to the simple key and connections made 

 from it with other wires via the inductorium 

 to some basilar portion of the instrument. 

 Next, a clean copper wire may be twisted or 

 clamped to some part of the top of the revolv- 

 ing drum and properly adjusted in such a way 

 that, if contact is just barely made with the 

 first wire the circuit will be completed for an 

 instant and the desired stimulus to the muscle 

 will be given at certain definite intervals, 

 always at exactly the same time on a uni- 

 form moving drum. In other words, the cir- 

 cuit is through the instrument and its action 

 becomes automatic. In the case of the Har- 

 vard kymographion such an arrangement can 

 not be used, for inasmuch as the drum is held 

 by a spring to the sleeve which in turn fits 

 over a tall vertical rod with its base resting on 

 the friction plate there is no external support 

 of the drum for attaching the wires. 



Accordingly, in order to produce such auto- 

 matic action on this particular type of ma- 

 chine, it is evident that some other device 

 must be used. The one which has been worked 

 out by the writer has been very successfully 

 used at the laboratory of the University of 

 Maryland during the past year. It consists of 

 a thin metal disk of about 18 mm. diameter 

 with a central opening large enough to admit 

 the screw of the spin-screw and is held in place 

 by means of the spin-nut against the head of 

 the sleeve of the kymographion. To the outer 

 under edge of this disk are soldered four 

 copper wires of two thirds mm. diameter and 

 about four em. in length, which radiate out 

 horizontally from the flat under surface of the 

 disk and revolve with the drum. The circuit 

 is then made complete by leading wires of 

 two thirds mm. diameter; one series from the 

 cell, first to the simple key and inductorium, 

 then to the milled head, or some other basilar 

 portion of the instrument; and the other to a 

 tall iron-stand where the insulated wire may 

 be wound around the upper portion of the up- 



right rod, in order to hold it in place with 

 about 6 or 7 cm. of the free end projecting 

 laterally from it and vertical to the rod. Just 

 enough of the insulation is removed from the 

 far end of the wire to make a small eye about 

 3 mm. in length and 2 mm. in width, and bent 

 so that the loop is directed downward. Into 

 this is placed a wire pendulum made from the 

 same kind of wire (uninsulated) having a 

 similar sized eye at one end and being 5 to 6 

 mm. in length. When properly adjusted this 

 wire arm projects out over the top of the drum 

 of the kymographion, so that the wire pen- 

 dulum just barely touches the outer extremi- 

 ties of the radiating arms as they come from 

 the disk and revolve with the drum, thus 

 making the electrical contact for just an in- 

 stant, and thereby stimulating the muscle 

 automatically. 



It is of the utmost importance that the eye 

 in the end of the wire and also the pendulum 

 and ends of the radiating wires from the disk 

 be kept clean and bright by means of emory 

 paper, so that the electrical contact may 

 always be at its highest point of efficiency. 

 I might also mention the fact, that, if the 

 pendulum is allowed to drag itself over the 

 radiating arms by being too long, it will 

 usually have a bouncing movement making 

 several contacts and giving as many stimuli 

 to the muscle. 



It is also of advantage, although not abso- 

 lutely necessary, to use a second simple key 

 between the wire containing the pendulum and 

 the cell, so that the circuit may be broken 

 without stopping the instrument, or moving 

 it away. However, one simple key in the 

 circuit is usually sufficient. 



T. L. Patterson 



Laboratory op Physiology, 

 University of Maryland 



accuracy in stating the occurrence of species 

 To THE Editor of Science: The difficulties 

 of exact scientific expression pointed out by 

 Mr. J. D. Kusen' relate to the loose use of 

 certain words in attempting to describe the 



1 Science, Vol. XXXV., June 14, 1912, pp. 930, 

 931. 



