238 APPENDIX 



effective apparatus, when only the time relations and the character 

 of movements are matters of concern, is the instrument which involves 

 the use of two tambours, a receiving and recording tambour. The 

 latter one is described above (12). 



A receiving tambour may be constructed especially for this purpose 

 as follows: Take a large thistle tube, cut off its funnel with 8 or 

 10 cm. of the tube, stretch across it loosely a piece of thin sheet 

 rubber and fasten this tightly as shown in Fig. 88, Steth. To the 

 middle of the rubber diaphragm fasten a long cork, using glue or 

 sealing-wax. 



The stethograph complete consists of a thoracic frame, as shown 

 in Fig. 58, and of the tambours, the recording tambour being held 

 by an extra support as usual. 



The thoracic frame is very simply constructed of pieces of half- 

 inch glass-pipe supported by a heavy stand and clamps as shown in 

 the figure. 



The receiving tambour is held in a clamp, its location upon the 

 bar being readily adjusted. The width of the frame and its height 

 are both easily adjustable. 



16. THE CHEST PANTAGRAPH. 



Fig. 59 shows the instrument, which is constructed of brass or wood 

 with brass or steel semicircle. The joints a, b, x, and y move easily 

 in the plane of the instrument. The semicircle, 40 inches in diam- 

 eter, rotates at x around the diameter t x. The point / is fixed to 

 a table. With / a fixed point all movements of t, the tracing point, 

 are accompanied by corresponding movements of r, the recording 

 point. The triangles /, r, b and /, t, a are similar triangles in all 

 positions of the instrument fb : fa : : fr : ft ; but fb : fa: : 1:5; there- 

 fore, the distance fr is always one-fifth the distance ft. 



The object of the semicircular arm is, of course, to permit the 

 tracing point t to be carried around the thorax. The seat upon 

 which the subject sits is adjustable in height and back and side 

 supports for the waist, so that the upper part of the body is not 

 allowed to waver from side to side, distorting the contour. If the 

 subject to be examined sit beside the table on which the instrument 

 is fixed; if the seat be adjusted in height to bring the plane of the 

 thorax to be examined into the plane of the instrument i. e., on a 

 level with the top of the table; if a sheet of millimetre paper be fixed 

 to the table under the recording pencil r; and if the tracing point t be 

 swept around the thoracic wall, a record of the chest contour will 

 be traced upon the paper. 



The accompanying Fig. 89 shows two such contours from healthy, 

 well-developed young men. Two millimetres in the figure equal one 



