178 THE WORK OF THE HEART. 



numerous animals die, thus, of themselves, cause disturbances in the circulation. 

 It was therefore suggested that the experiments be repeated with a substance 

 that truly is chemically indifferent, or perhaps with the microscopic demonstra- 

 tion of particles introduced into the circulation (such as heterogeneous blood- 

 corpuscles, milk-globules or pigment-granules) . Accordingly, L. Hermann, in 1884, 

 selected the innocuous sodium ferrocyanid. Wolff, thus found the duration of the 

 circulation in the rabbit to be 5^5 seconds, and it is therefore probable that in other 

 animals also the time is shorter than that given by Vierordt. Landois injected 

 mammalian blood-corpuscles into the lateral abdominal vein of frogs and searched 

 for them microscopically on the opposite side. In this way he found the time from 

 7 to 1 1 seconds, v. Kries has recently expressed some doubt as to the general 

 applicability of the method even from a physical standpoint. The substances first 

 encountered .are carried along only in the axial stream of the blood-vessels, and 

 no conclusion, therefore, can be drawn from their appearance as to the circulation 

 of the entire mass of the blood. 



Stewart employed a different method. If the electrical resistance offered by 

 an unopened artery is first determined with a galvanometer, and at a given moment 

 some saline solution is injected into the circulation, the galvanic resistance will be 

 diminished when the saline blood passes through the section in communication 

 with the galvanometer. The instant when this takes place is also noted. In this 

 way Stewart found for the lesser circulation about one-fifth of the entire duration 

 of the circulation ( = 10.4 seconds, in the rabbit and in the dog). The duration of 

 the circulation in the kidney was 8 seconds, in the liver 3.8 seconds. 



A venous state of the blood increases the duration of the circulation. 



Pathological. In the presence of fever the duration of the circulation appears 

 to be increased. 



THE WORK OF THE HEART. 



Following the method of Johann Alfons Borelli and Daniel Passavant, Julius 

 Robert v. Mayer estimated the work of the heart according to physical principles. 

 The work performed by a motor is expressed in kilogrammeters, that is, the num- 

 ber of kilos that the motor is capable of raising to the height of i meter in the 

 unit of time. 



Robert v. Mayer calculated that the left ventricle propels with each systole 

 0.188 kilo of blood, and, in order to raise it into the aorta, has to overcome the 

 pressure existing in that vessel, corresponding to a column of blood 3.21 meters 

 in length. The work of the ventricle at each systole is, therefore, equivalent to 

 0.188 X 3-21 = 0.604 kilogrammeter. Allowing 75 systoles for each minute, the 

 work of the left ventricle in 24 hours is equal to 0.604 X 75 X 60 X 24 = 65,230 

 kilogrammeters. The work of the right ventricle is only about of that of 

 the left, or, in other words, about 21,740 kilogrammeters. The work of the two 

 ventricles taken together is, therefore, 86,970 kilogrammeters. The work per- 

 formed by a laborer during 8 working-hours equals 300,000 kilogrammeters, 

 thus not quite four times as much as that of the heart. As all of the kinetic 

 energy of the heart is converted by the resistance encountered within the circula- 

 tion into heat, the work of the heart must result in supplying the body with 

 heat: 425.5 grammeters correspond to i unit of heat, that is, the same force 

 that is capable of raising 425.5 grams to a height of i meter is also capable 

 of raising the temperature of i cu. cm. of water i C. The body, therefore, 

 acquires by the conversion of the kinetic energy of the heart about 204,000 

 units of heat. 



As i gram of coal yields 8080 units of heat when consumed, the working heart 

 accomplishes as much for the body as if more than 25 grams of coal were burned 

 in it for the production of heat. The values given would be much smaller if the 

 capacity of the ventricles were assumed to be smaller; for example, 60 cubic centi- 

 meters; on that basis the work of the heart would be equivalent only to 20,000 

 kilogrammeters, or -^ of the entire muscular work of the body. 



THE MOVEMENT OF THE BLOOD IN THE SMALLEST 



VESSELS. 



In the study of the movement of the blood in the smallest vessels 

 microscopic observation of transparent portions of living animals is the 



