78 GENERAL PROPERTIES OF LIVING TISSUES 



The writing point rubs off the soot in its path 

 and leaves a white magnified tracing of the 

 muscle's change in length or whatever dimen- 

 sion is the subject of record. The paper is then 

 removed, drawn through a saturated solution of 



paper. The extra length allows the edge of the overlap to be 

 gummed to the paper below, permits the paper to be removed 

 from the drum by cutting through the overlap parallel to the 

 mucilage, the surface of the drum being protected from the 

 knife by the underlying paper, and provides an unsmoked 

 surface by which the paper can be handled on its removal from 

 the drum. The drum should be laid in the centre of the strip 

 of paper, the gummed edge to the left, and the axis of the drum 

 precisely at right angles to the long axis of the paper ; the 

 mucilage should be moistened, and the ends of the paper 

 brought around and fastened. If the paper is awry, the sur- 

 face will not lie uniformly against the drum and the record 

 will be deformed. The drum should now be placed in the 

 smoking apparatus, revolved uniformly and not too fast, 

 brought over the gas flame, lowered just below the upper edge 

 of the flame, and covered with a chocolate brown layer of soot, 

 beginning at the operator's left hand and passing gradually to 

 the right. The speed should be such that one passage from 

 left to right shall suffice. To trim . the edges, hold the drum 

 in the left hand, inclined downwards, and pass a sharp knife- 

 blade around the lower edge. The handle of the knife should 

 be kept lower than the blade, to avoid tearing. In removing 

 the paper from the drum, hold the drum in the air with the 

 left thumb pressed on the edge of the paper near the overlap, 

 and cut through the overlapping edge near the mucilage. The 

 loosened paper will hang down and may then be seized by the 

 unsmoked overlap. In recording, let all the curves begin near 

 the overlap. Attention to these details is indispensable to the 

 best technical results. 



