190 PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



apparatus is more or less perilous. In association experiments it is 

 particularly inexpedient. It became necessary, therefore, to devise 

 some form of pulse-recorder which would act at a distance, while still 

 permitting definite correlation with the other data of the experiment. 

 As our solution of the problem may be of general use, we shall give it 

 in some detail. The conditions seemed to indicate a device by which 

 the mechanical pulse-wave should break an electric contact, which 

 would in turn activate an electric marker. That was the plan which 

 we adopted. The Wiersma 1 hand sphygmograph gave remarkably 

 large pulse-oscillations and seemed consequently admirably adapted to 

 our purpose. Dr. Wiersma's plan was to bind the hands of the subject 

 around a rubber capsule. Since the bandage was rigid, each pulsation 

 forced the air out of the capsule to the recording tambour. Personal 

 experience with such a binding showed that after 15 minutes it might 

 become almost intolerable. But even if it were quite comfortable, it 

 would obviously be something of an annoyance and a considerable 

 waste of time to bind and unbind a subject's hand several times during 

 the course of a 3-hour experiment. In view of these difficulties, we 

 experimented to find some sort of a clamp which would slip on and off 

 the subject without delaying the experiments. 



With the help of Dr. Carl Tigerstedt, at that time Research Associate 

 of the Nutrition Laboratory, we tried various devices of plaster of 

 Paris and other plastic forms. But an even simpler device composed 

 of reinforced felt cushions and a light "C : ' clamp proved equally satis- 

 factory. As a transmitting capsule we used about 12 cm. of soft-rubber 

 tubing about 2.5 cm. in diameter, which was closed at both ends with 

 rubber stoppers and connected to a Marey tambour by rubber tubing. 

 In use, this transmitting capsule was grasped firmly in the subject's 

 left hand, which was then inserted in the clamp between the felt 

 cushions, and relaxed. Pulse-waves of large amplitude may thus be 

 transmitted to the tambour recorder. Some subjects regularly give 

 much larger oscillations than others. With a recording lever of 10 cm., 

 Dr. Tigerstedt gave curves with an amplitude of more than 2 cm.; 

 5 to 6 mm. is more common and is satisfactory. An amplitude of less 

 than 4 mm. is sufficient only if the transmitting device is carefully 

 adjusted. 



The first device by which these pulse-waves operated to make and 

 break the transmitting electric circuit was a platinum contact between 

 the tambour lever and a horizontal rest which the lever just touched 

 at the lowest point of each oscillation. But when the moving parts 

 were sufficiently delicate so as not greatly to diminish the amplitude 



'Thanks to the kindness of Professor Wiersma, one of us was shown the working of his ingenious 

 hand sphygmograph at Groningen. At the time of our going to press we are acquainted only 

 with the brief description of this apparatus with accompanying curves given in the Program of 

 the Communications and Demonstrations of the Ninth International Congress of Physiologists at 

 Groningen, 1913. 



