\ 



Curves from a Case of Transient Heart Block. 25 



auricular beat, but somewhat later there was complete dissociation 

 between the two pairs of cavities. Before the patient left the 

 hospital, the relation between the auricles and ventricles was 

 normal. Electric curves were taken on December 19, 191 1, when 

 the ventricles responded to every auricular contraction. 



The curves which are of interest date from the period of com- 

 plete auriculo-ventricular dissociation. Each ventricular complex 

 is represented by R-, S-, and 7"-waves. They vary from each 

 other in that, when the R- is large, the 5-wave is small; and that 

 when the .S-wave is large, the i?-wave is small. The i?-wave 

 gradually increases in size and then gradually diminishes, when 

 the 5-wave gradually increases in size and as gradually diminishes. 

 If the apexes of succeeding R- and S-waves, i. e., the significant 

 wave in each complex were joined, a waved line would result. So 

 diagrammatic a sequence as this did not occur frequently, but 

 there was a tendency to approximate to this description. Some- 

 times the transition from complexes of one type to those of another 

 was abrupt. The time between the complexes was almost equal, 

 except at points of transition, when it was reduced. 



It is concluded from the variation in the shape of the complexes, 

 that they are responses to stimuli arising at levels in the heart 

 varying from some supraventricular position to the apex. The 

 explanation of the shortened time at points of transition is difficult. 

 No hypothesis yet suggested is satisfactory. The fact that there 

 was merely a temporary and not a permanent dissociation may be 

 a significant factor, although the P-R interval associated with the 

 transitions is not of uniform length. (P is the wave representing 

 auricular systole.) 



8 (627) 



Further observations on the tolerance of gases by the 

 circulatory apparatus. 



By J. P. Atkinson and c. B. fitzpatrick. 



[From the Department of Health, City of New York.] 



In the New York Medical Journal of November 26 and at the 

 New Haven meeting of December, 1 910, we gave observations on 

 the quantities of gas (air) tolerated and the apparent relation of 



