136 THE DURATION OF THE CIRCULATION. 



by the right carotid, right subclavian, the two coronary arteries, and the aorta below the origin 

 of the innominate artery. He estimated that with every systole of the heart, 172 cubic centi- 

 metres (equal to 180 grammes) of blood were discharged into the aorta ; this, therefore, must be 

 the capacity of the left ventricle (compare 83). 



92- THE DURATION OF THE CIRCULATION.- The time required by the 

 blood to make a complete circuit through the course of the circulation was first de- 

 termined by Hering (1829) in the horse. He injected a 2 per cent, solution of potas- 

 sium ferrocyanide into a special vein, and ascertained (by means of ferric chloride) 

 when this substance appeared in the blood taken from the corresponding vein on the 

 opposite side of the body. The ferrocyanide may also be injected into the central 

 or cardiac end of the jugular vein, and the time noted at which its presence is 

 detected in the blood of the peripheral end of the same vein. Vierordt (1858) 

 improved this method by placing under the corresponding vein of the opposite side 

 a rotating disc, on which was fixed a number of cups at regular intervals. The 

 first appearance of the potassium ferrocyanide is detected by adding ferric chloride 

 to the serum which separates from the samples of blood after they have stood for 

 a time. The duration of the circulation is as follows : 



Hedgehog, . 7*61 seconds. Duck, . . 10-64 seconds. 

 Cat, . .6*69 ,, Buzzard, . 673 ., 



Goose, .10-86 ,, | Fowl, . . 5 17 ,, 



Results. When these numbers are compared with the frequency of the normal 

 pulse-beat in the corresponding animals, the following deductions are obtained : 



(1) The mean time required for the circulation is accomplished during 27 heart- 

 beats, i.e., for man = 32*2 seconds, supposing the heart to beat 72 times per 

 minute. 



(2) Generally, the mean time for the circulation in two warm-blooded animals 

 is inversely as the frequency of the pulse-beats. 



Modifying Conditions. The time is influenced by the following factors : 



1. Long vascular channels (e.g., from the metatarsal vein of one foot "to the other foot) re- 

 quire a longer time than short channels (as between the jugulars). The difference may be equal 

 to 10 per cent, of the time required to complete the entire circuit. 



2. In young animals (with shorter vascular channels and higher pulse-rate) the time is 

 shorter than in old animals. 



3. Rapid and energetic cardiac contractions (as during muscular exercise) diminish the time. 

 Hence rapid and at the same time less energetic contractions (as after section of both vagi), and 

 slow but vigorous systoles (e.g., after slight stimulation of the vagus), have no effect. 



C. Vierordt estimated the quantity of blood in a man, in the following manner : In all 

 warm-blooded animals, 27 systoles correspond to the time for completing the circulation. 

 Hence, the total mass of the blood must be equal to 27 times the capacity of the ventricle, i.e., 

 in man, 187 "5 grms. x 27 = 5062*5 grms. This is equal to r V of the body-weight in a person 

 weighing 65 '8 kilos, (compare 49). 



It is not to be forgotten that the salt used is to some extent poisonous, but Hermann uses the 

 corresponding innocuous soda salt (25 per cent). 



Pathological. The duration of the circulation seems to be increased during septic fever 

 (A Wolff). 



93. WORK OF THE HEART. The left ventricle expels 0-188 kilo, of blood 

 with each systole, and in doing so it overcomes the pressure in the aorta, which is 

 equal to a column of blood 3 21 metres in height. [The amount of blood expelled 

 from each ventricle during the systole is about 180 grms. (6 oz.). It is forced out 

 against a pressure of 250 mm. Hg. = 3*21 metres of blood.] The work of the heart 

 at each systole is 0*188 x 3*21 = 0604 kilogramme-metre. If the number of beats 

 = 75 per minute, then the work of the left ventricle in 24 hours = (0*604 x 

 75 x 60 x 24) = 65,230 kilogramme-metres ; while the " work " done by the right 

 ventricle is about one-third that of the left, and therefore = 21,740 kilogramme- 

 metres. Both ventricles do work equal to 86,970 kilogramme-metres. A workman 

 during eight hours produces 300,000 kilogramme-metres, i.e., about four times as 



