APPENDIX A. 



315 



button of about 4 or 5 cm. It may be fixed to the hard 

 wood or fiber base with three staples and the base in turn 

 fixed, as indicated in the figure, to an iron rod about 1 cm. 

 thick by 30 cm. long. A hole is bored through the base in 

 the middle of the cone. A pulley whose plan and elevation 

 are given in Fig. 58 b and c, fastened to the under surface 

 of the base serves to change the direction of a cord which 

 is tied to a ring in the hard rubber button. 



12. The belt=spirograph. 



The apparatus here described was contrived to over- 

 come as far as possible the objections which may be raised 



FIG. 59. 



FIG. 59. The Belt-spirograph for quantitative determination of varia- 

 tions in chest girth. 



to the previously used instruments for this purpose. Note 

 in the first place that the wide elastic belt will follow faith- 

 fully every movement of the chest wall, not sinking into 

 the soft tissues during inspirations; second, the almost in- 

 elastic fish cord will transmit the movement of the thorax 

 much more accurately than elastic air inclosed within 

 elastic conductors. 



The 59 a, b and c figures show the construction of 

 the belt spirograph: (a) The 2-3 cm. wide, elastic belt 



