174 



Scientific Proceedings (76). 



coronary arteries of an isolated normal rabbit heart, usually pro- 

 duces the following series of phenomena: 



1. An initial tachycardia, lasting about three minutes, suc- 

 ceeded by 



2. A period of apparently normal heart action, lasting about 

 five minutes, succeeded by 



3. A secondary tachycardia, lasting about two minutes, 

 ushering in 



4. A period of decreasing rate and strength of heart action, 

 increasing irregularities, etc., usually ending in inactivation of the 

 heart in about ten minutes. 



If goat serum is separated into diffusible and non-diffusible 

 fractions by dialysis through a celloidin membrane, and the two 

 fractions are tested independently, the following results are usually 

 obtained : 



1. The diffusible substances tested in 7 per cent, to 10 per cent, 

 dilution usually produce an initial tachycardia indistinguishable 

 from the tachycardia from the whole serum. This is succeeded 

 by a period of regular rate and rhythm usually lasting for over 

 an hour. 



2. The non-diffusible substances (serum colloids) similarly 

 tested usually give no initial tachycardia, the rate and rhythm 

 continuing unchanged for about ten minutes. There is then usual- 

 ly a slight secondary tachycardia, ushering in a period of decreasing 

 heart action, usually ending in inactivation in about fifteen min- 

 utes. 



The secondary tachycardia is always accompanied by a pro- 

 gressively decreasing rate of perfusion through the coronary 

 arteries, and beginning myocardial edema. We are therefore 

 inclined to attribute the secondary tachycardia and subsequent 

 heart-death to a breaking down of the capillary defenses (increased 

 capillary permeability), allowing the foreign colloids to pass out 

 of the capillaries into the tissue spaces, thus coming into direct 

 contact with the essential myocardial cells. 



