Pulse and Respiration. 97 



in the post-tetanus division the shortening of the pulse cycle is due 

 almost entirely, so far as preliminary measurements reveal, to a short- 

 ened duration of the diastole (distance from end of T to beginning of 

 P), as the distance from the beginning of P to the end of T (systole) 

 remains quite constant. It is a well-recognized fact that the diastole 

 is the portion of the pulse cycle that shows the greatest percentage of 

 change in length with the transition from rest to exertion and from exer- 

 tion to rest under conditions of such short periods of activity. In our 

 measurements, however, it was not practicable to begin or end the 

 muscular tension with a fixed relation to diastole. Since the vagus 

 mechanism has a latency in its action, it occasionally happened that 

 tetanus began at such a point during systole or immediately following 

 it that a particular pulse cycle, although counted as belonging to the 

 tetanus division, shows no conspicuous change in the length of its 

 diastole; i. e., the action of the vagus does not appear until the next 

 cycle, which is the second for that section of the record. Illustrations 

 of this are found in table 17, June 29, period 3, record 2, and June 30, 

 period 2, both records. Usually the first cycle in the tetanus division is 

 shorter by several hundredths of a second than that immediately pre- 

 ceding, i. e., the last cycle in the pre-tetanus division. The fact that 

 the P-R time is the latter part of the distance which we are measuring 

 for each pulse cycle must be remembered when considering the data 

 at the transition point in relation to vagus action. 



In tabulating these data it is not expedient to use the form employed 

 for other measurements, for even the most condensed form of table is 

 necessarily large and unwieldy. Table 17 follows the same general 

 arrangement as the individual record. The left section of the table 

 shows the duration of individual pulse cycles preceding tetanus, the 

 central section the duration of those during tetanus, and the large sec- 

 tion at the right the post-tetanus pulse cycles. The beginning of 

 tetanus is made the starting-point for the measurement of the record. 

 Six pre-tetanus cycles were measured; these from the start of tetanus 

 are numbered in order from right to left. The cycles which came in the 

 tetanus period are numbered from left to right and likewise for the post- 

 tetanus period from the end of tetanus. For the sake of clearness the 

 cycles have been numbered in A of figure 11, the same numbers being 

 given in the headings of the columns in table 17. The pre-tetanus sec- 

 tion of the record contained more than 6 cycles, but the cycles measured 

 immediately preceding the beginning of tetanus were limited to this 

 number. The tetanus occupied approximately 5 seconds; the number 

 of pulse cycles which fell within these limits varied from 6 to 9. Of 

 the 60 records which enter into table 17, 7 contained only 6 pulse 

 cycles in the tetanus section, 10 records contained 9 cycles, and 16 

 others contained 8 cycles. On July 4, the last alcohol day, the pulse 

 rate tended to be faster, hence during the 5 seconds of tetanus more 



