384 APPENDIX. 



drums moved by some kind of motor are essential. Drums moved by clock- 

 work, however convenient for individual work, are not suitable for students' 

 purposes. Hence various devices are used so that many men are enabled to 

 work at separate drums at the same time. 



Motor, — One has first to consider what form of motor one shoulQ use co 

 drive the drums. Some use a small gas-engine, others use a water-motor, as, 

 for example, the Swiss form of motor made by Schmidt, or the Thirlmere form, 

 while others prefer an electric motor where electricity is available. Such an 

 electric motor is made by Siemens and Halske, Berlin, but the initial cost of 

 this apparatus is considerable. 



Transmission of Motion. — Next arises the question as to how the motion is 

 to be transmitted to the drum. This is don^ in various ways. In the 

 Cambridge system, which is adopted foi some of the drums in the Physio- 

 logical D'^-partment of Owens College, the motion is transmitted from the 

 motor — gas-engine or Thirlmere water-motor placed in the basement — by means 

 of an endless quick-running cord. This method is extremely convenient, and 

 the drums are so made that they can be readily arrested, and can also be 

 made to move at diflferent speeds. 



Some use shafting fixed on a support on the wall or ceiling or on a table. 

 To the shaft are fixed coned pulleys, i.e., wheels of different diameters, whereby 

 a good range of speeds cac be obtained. 



Recording Drum. — Next comes the form of drum to be used. In the 

 Cambridge arrangement the drum can be raised or lowered on a vertical axis 

 by means of a clutch, while the drum itself can be set in motion or arrested by 

 means of a handle on the driving pulley. The rate of movement can also be 

 changed as desired. 



Prof. Schafer has also designed a form of drum which is moved by a short 

 cord passing over coned pulleys fixed to a long rod placed on bearings fixed to 

 a tible and moved by a water-motor. It is made by Backhouse, Physiological 

 Department, University College, London. 



The Oxford pattern is somewhat different from this, and is made by Butler, 

 Physiological Department, Oxford. 



In Hering's large kymographion there is a long sheet of paper (2 metres) 

 stretched over an iron framework, which is moved by clockwork driven by a 

 weight. In University College, London, to this framework a small cogwheel 

 is adapted whereby this arrangement can easily be driven by an ordinary 

 motor. It is specially useful for research work where a moderate or slow speed 

 of the recording surface is required. 



In the "physiological recording drum" (fig. 288), as made for Dr 

 Sherrington, the cylinder is 6 inches by 6 inches, and is so arranged that it 

 can be used in a vertical or horizontal position, and has a lever by which it 

 can be instantly started or stopped at any portion of a revolution. The cone 

 pulley gives a good range of speeds. The brass cylinder is turned perfectly 

 true in a self-acting lathe, and has about 5 inches vertical adjustment. It is 

 easily removed for the purpose of blacking, and can be run by any light motor 

 or clockwork, as desired. The whole is mounted upon a substantial cast-iron 



