The circulation and sleep : experimental investigations accompanied by an atlas / by John F. Shepard.

  • Shepard, John F. (John Frederick), 1881-
Date:
[1914], ©1914
Catalogue details

Licence: In copyright

Credit: The circulation and sleep : experimental investigations accompanied by an atlas / by John F. Shepard. Source: Wellcome Collection.

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    ment set evenly on the bone around the trephine. The other form was more analogous to that used by Mosso and Brodmann. A plaster of Paris cast was made from the subjects’ forehead. On this a shallow, hard rubber cup was built, covering the position of the trephine. A metal tube led out through the top side of the cup, and a rubber tube connected this to a piston recorder. The edge of the cup was of soft rubber. When this was covered with vaseline, and pressed steadily against the forehead, it formed a small, perfectly air-tight chamber over the opening in the skull. We shall speak of this as the second form of brain plethysmograph. Only a single broad bandage tied around the head from front to back, was necessary to hold either form in place on the second subject. Two breathing tracings were usually recorded, one from the chest, the other from the abdomen. A Sumner pneumograph connected to a Marey tambour was used for each. In all breathing curves, the fall is due to inspiration, the rise to expiration. It will be noticed that all brain tracings were written by a piston recorder. In fact, all pulse records, whether from the brain or elsewhere, were made by means of this instrument. The form used was a modification of that described by Lom- bard and Pillsbury in Vol. III of the American Journal of Physiology. As in their work, the piston was made of plaster of Paris. But the ball and socket joint did not work satisfactorily for me. A slight inequality in the weight of opposite sides of the piston, due to a difference in absorption of oil, a particle of dust or a bubble of air in the oil, seemed sufficient to cause the piston to tip and bind. It would often catch if the change of volume moved it much above or below the level line, probably because the oblique position of the piston rod pressed it towards one side of the tube. ‘Whenever the piston began to tilt for any reason, the immediate increase of friction would nearly always aggravate rather than correct the difficulty. To prevent this, I cemented the piston-rod firmly into the center of the piston. Under these circumstances the disk could be cut even thinner than that used by Lombard and Pillsbury. It was made just small enough in diameter to turn almost or quite over in the tube without binding. With this arrangement there was a slightly greater chance that a sudden change of pressure would force a bubble of air past the piston and produce an artificial rise or fall. But such an event seldom occurred, particularly when a somewhat thicker oil was used; and in any case, the experienced observer could easily detect it. Several recorders were made, of different sizes, ranging from four mm. to eleven mm. in the diameter of the piston. Kerosene was used with the smaller sizes and kerosene mixed with a thicker oil for the larger. When new pistons are made, it is well to keep them for a time in oil. With one of the recorders, I used a phosphor-bronze writing lever made by Lombard and Pillsbury. For the others, I made levers of thin celluloid. This material seems to me to meet the requirements more fully than the bronze. The lever was cut and bent so that when suspended on the pin used as axis and without the piston-rod attached, it would balance. When connected for use, therefore, the weight of the oiled piston and piston-rod tended to cause the