84 GENERAL PROPERTIES OF LIVING TISSUES 



kymograph clockwork is removed, and then the entire 

 bench together with its drums is placed horizontally 

 in the smoker frame (Fig. 20). 



Fig. 20. The smoker, showing the long paper kymograph in place. The 

 paper is smoked with an oil lamp having a four inch wick. Near the 

 stand are the handle with which the drum is revolved to carry the paper 

 over the lamp flame, and the two rods which are inserted in the kymo- 

 graph clockwork when the latter is used independently of the long paper 

 arrangement. 



The graphic record involves the use of appa- 

 ratus. It never should be forgotten that the use 

 of apparatus always introduces more or less 

 error. In every experiment the apparatus 

 should be criticised sharply. The numerous 

 imperfections which such scrutiny will bring 

 to light are of two sorts, the errors that may 

 be neglected, arid the errors that may not be 

 neglected without seriously impairing the value 

 of the method for the purpose in hand. For 

 example, a count of the pulse rate with an ordi- 

 nary watch will usually be incorrect by one or 



