74 



Scientific Proceedings (120). 



going on while the blood phosphate is still in the rachitic range. 

 We therefore conclude that a definite deposition of calcium salts 

 may occur before the blood phosphorus regains its normal level. 

 We have as yet no experiments in which the rats were carried 

 through till the healing process was complete, but if we may draw 

 analogies from the work of Howland and Kramer on human rick- 

 ets, we ought to find that when healing is complete the blood 

 phosphate will regain and maintain its normal level. It seems 

 therefore that calcification is not directly controlled by the level 

 of the blood phosphate. Experiments are, however, in progress 

 to determine the nature of the relation between these two factors. 



80 (1827) 



Experiments with quinidine on conduction and on the refractory 

 period in the dog's heart. 



By ALFRED E. COHN and ROBERT L. LEVY. 



[From the Hospital of the Rockefeller Institute for 

 Medical Research, New York City.] 



These experiments are based on the theory of fibrillation 

 developed by Garrey and Mines on the suggestion of A. G. Mayer 

 and recently elaborated by T. Lewis. The theory, although it 

 illustrates best the condition known as flutter, is directly applicable 

 also to the state of fibrillation. In the normal heart the stimulus 

 for contraction arises at the sinus node and passes in a radial 

 fashion to the rest of the muscle of the auricle. In flutter, and 

 in fibrillation, there is apparently no fixed point at which the 

 stimulus originates. It appears to be dislocated from the node 

 but it is not yet known what activity goes on in this structure 

 when the abnormal rhythm prevails. Instead of the usual 

 arrangement, an excitation wave courses continuously through the 

 muscle of the auricle, usually over a circular path about the open- 

 ings of the great veins, as Lewis's experiments show. In order 

 that a continuous circuit may be maintained it appears to be 

 necessary (1) that the path shall have a sufficient length; (2) 

 that the rate of passage shall be sufficiently slow, and (3) that 

 when the stimulus returns to its starting point, the muscle is 

 ready to receive it. It is clear, on this plan, that: (1) if the muscle 



