200 IOWA ACADEMY OF SCIENCE Vol. XXIX, 1922 
commonly illustrated and analyzed in some of the many standard 
texts . 1 
In the rapid drum method several mechanical devices have 
been used by various investigators, but the one found easily 
adapted to this end consists of a Harvard type moist chamber 
in which the muscle is mounted in such a way as to move a 
light writing lever. The primary circuit is automatically “made” 
and “broken” by the rapidly revolving drum. This is done by 
cams rotating upon the drum spindle coming into contact with 
a circuit breaker (Zimmermann type) mounted upon the clock 
housing. Obviously upon analysis, records obtained by this 
method have some advantages over those obtained by the other 
in that they give valuable data as to the relative amplitudes of 
responses, and in addition the accompanying rate and duration 
of various phases of the oncoming process can be found es- 
pecially when correlated with time intervals as recorded by a 
chronometer. They have some disadvantages, however, for since 
the stimuli fall at the same point as the drum rotates, the trans- 
cribed lines representing successive responses are more or less 
superimposed upon one another with consequent masking, es- 
pecially in the Contraction phase. In some cases this masking 
of individual responses is more serious than in others, due no 
doubt to differences in rate of metabolic reorganization, and when 
this is true it renders the record by this method difficult to analyze. 
Another objection is that the crest and trough representing any 
one cycle of responses are so far removed from one another, due 
to the rapid rotation of the drum, that indexes of such important 
phases as primary contracture or relaxation are impossible to 
accurately ascertain. Curves illustrating this mode of procedure 
are found quite generally, especially in the English texts . 2 
With such considerations in mind it seems desirable to combine 
the two classical procedures and obtain simultaneously records 
by both methods using the same irritable tissue. Especially such 
a procedure is of value in demonstration where by careful ob- 
servation and notation the details in one can be made to supple- 
ment the other at critical- points. By such a method also diffi- 
culties from the comparative analysis of the various phases are 
obviated since the same muscle produces them simultaneously in 
both. 
1 See Howell, Textbook of Physiology, 7th ed., pp. 33-34, 1919; also Brubaker, Text- 
book of Physiology, 4th ed., pp. 70'-7l, 1912. 
2 See especially Schafer, Textbook of Physiology, V. 2, 1900, p. 388; fig. 216; Star- 
ling, Principles of Human Physiology, 1912, p. 234; Halliburton, Handbook of 
Physiology, 1920, p. 98. 
