X. SPECIAL COLLECTIONS. 819 



in a little box suspended on a cross-bar between electrodes with knobs, which 

 are to be moved so far apart that the passing electricity constitutes only one 

 spark. In order to see or to hear the spark, a Leyden jar is inserted in the 

 circuit ; the shock is felt as unipolar conduction without an inserted Leyden 

 jar. 



On the stimulus being received, it is responded to by the hand moving a 

 copper arm of a wooden cylinder with registering spring. By this con- 

 trivance, under similar objective and subjective conditions, the physiological 

 time (the time between stimulation and response) can be determined alter- 

 nately for impressions of vision, of hearing, and of touch at various places of 

 the skin. 



A dilemma may be put. Electrodes are applied right and left on the skin, 

 and the horizontal arm of the wooden cylinder struck in corresponding 

 direction. In a similar manner, by a conventional response, a decision may be 

 made between red and white light. In both cases response may be forbidden 

 for one colour or for stimulation on one side. Instead of responding with the 

 hand, the voice may be used acting on the phonautograph, and the physio- 

 logical time determined in both ca-;es. On the spark passing in the box, and 

 making transparent letters visible, the physiological time for recognising 

 these letters may be registered and compared with the time for simple light 

 perception, etc. 



The second ring has only a small conducting plate, upon which, at the 

 rotation of the cylinder, the constant current is closed and broken, after con- 

 tact with the electrodes of the induction current has followed. Thus, by 

 sliding this second ring, sooner or later after the first spark, a second is 

 made to pass, perforating the chronoscopic line, and at the same time, either 

 visible in the second compartment of the box, audible, or sensible at another 

 part of the skin. So we learn the time between two impressions on the same 

 sense, or on two different senses, which enables us to judge about the priority. 



In order to prevent, under all circumstances, the sparks from passing from 

 one ring to the other, a somewhat greater distance between the rings is 

 desirable. 



PROFESSOR MAREY'S APPARATUS FOR OBSERVING AND REGIS- 

 TERING PHYSIOLOGICAL AND MECHANICAL PHENOMENA. 



3997. 1. Cardiac sounds for indicating the pressure in the 

 cavities of the heart. A. Sound for the right heart. B. Sound 

 for the left heart. C. Sound for showing negative pressures. 

 D. Sphygmoscope. (The corresponding tracings are given in 

 Plate I., 1-4. 



2. Explorator for the heart of the rabbit. (Plates 2 and 2 

 quater.) 



2A. Explorator for the human heart. (Plate II.) 



3. Explorator for the pulse (sphygmograph of transmission). 

 (Plate III.) 



4. Explorator for the respiratory movements. (Plate IV.) 



5. Myographic pincers. 



5 A. Myographic pincers, another pattern. 



6. Explorator for the investigation of to-and-fro movements, 

 such as those of locomotion (of the horse), and of flight (of birds). 

 (Plate VI.) 



3 F 2 



