Bauhaus-Universität Weimar

Description of a Piston Recorder for Air Connections [From the Journal of Physiology, Vol. VII, No. 4, Offprint]
Ellis, F. W.
(PL XI. Fîg. I). The tube B is held vertically by the clamp 0. A is 
the paraffin piston, D is a perforated stopper through which passes the 
glass tube E. The tube E should project above the level of the stopper 
in order to prevent any oil that may collect at the bottom of the tube B 
from running into the tube E. G is the slender piston rod of glass 
terminating above in the paper stirrup H presently to be described. 
M is a band of thin brass encircling the glass tube. The ends of the 
band are bent at right angles to the tangent of the circle formed by it. 
A piece of lead wire L is soldered to M ; this can be bent in any 
direction. A screw N is fastened to the other extremity of the lead 
wire. 0 is a piece of wrood or brass shown in a front view at Fig. 3. 
P is a small disc of cork with a pin axis. The sharpened extremities 
of the axis are received into corresponding depressions in the two lateral 
screws. The needles I and Q are thrust into this cork. The needle Q 
has a thread cut upon it ; and the small counterpoise JR may be screwed 
backwards and forwards. The needle I may be attached to the paper 
marker K directly or by means of an intermediate piece of straw, 
broom-corn, or other light substance. In constructing very delicate 
recorders I have made the entire lever of paper with the exception of 
the small piece of needle necessary to attach it to the cork disc. 
A long paper marker slightly bent works with very little friction against 
the smoked paper upon the recording cylinder, and is greatly superior 
to tinsel for delicate work. The connecting joint between the piston rod 
and the recording lever must, necessarily, be a very delicate one : the 
motion of the lever must not be impeded by it ; at the same time, the 
joint must not be at all loose. A very satisfactory joint may be 
constructed as follows : A small piece of paper (H, seen in the front 
at Fig. 2) has a small hole punched in its centre. A piece of thin 
rubber or calves’ peritoneum is pasted over the hole with mucilage. 
The paper stirrup is fastened to the piston-rod by means of sealing-wax. 
The needle I is thrust through the membrane covering the hole in the 
The pistons are very easily constructed. Small pistons may be cut 
out of the paraffin with a sharp cork-borer. Larger pistons can be 
readily made with a foot lathe. A small hole is made in the centre of 
the piston, and into this is cemented the piston-rod by means of a 
hot wire. The rubber tube F connects the recorder with the other 
apparatus with which it is used. Between this apparatus and the 
recorder there must be a lateral opening to be opened or closed as 
required. In adjusting the apparatus it is necessary that this should


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