348 CIRCULATION. 



treating of the capacity of the different cavities of the heart, 

 it has been noted that the left ventricle, when fully distend- 

 ed, contains from five to seven ounces. Assuming that at 

 each systole the left ventricle discharges all its blood, except 

 perhaps a few drops, and that this quantity in an ordinary- 

 sized man is five ounces (for in the estimates of Robin and 

 Hiffelsheim, the cavities were fully distended, and contained 

 more than under the ordinary conditions of the circulation), it 

 would require fifty-eight pulsations for the passage through 

 the heart of the entire mass of blood. Assuming the pulsa- 

 tions to be seventy-two per minute, this would occupy about 

 forty-eight seconds. 



We have given elsewhere the opinions of various physiol- 

 ogists on the quantity of blood in the body, and the capacity 

 of the cardiac cavities, and shall not discuss the discordant 

 views on the " duration of the circulation," as each is based 

 on different opinions regarding the two essential questions in 

 the problem. As the quantity of blood in the body is sub- 

 ject to certain physiological variations, there should be cor- 

 responding variations in the duration of the circulation, 

 which it is unnecessary to take up fully in this connection. 



The almost instantaneous action of certain poisons, which 

 must act through the blood, confirms our ideas with regard 

 to the rapidity of the circulation. The intervals between the 

 introduction of some agents (strychnine for example) into the 

 circulation, and the characteristic effects on the system, have 

 been carefully noted by Blake, 1 whose observations coincide 

 pretty closely in their results with the experiments of 

 Hering. 



The relation of the rapidity of the circulation to the fre- 

 quency of the heart's action is a question of considerable in- 

 terest, which was not neglected in the experiments of He- 

 ring. It is evident that if the charge of blood sent into the 

 arteries be the same, or nearly the same, under all circum- 



1 Edinburgh Med. and Surgical Journal, 1840, vol. liii., p. 35, and 1841, vol. 

 Ivi., p. 412. 



