FIBRINE IN THE HUMAN BODY. 181 



traction of the heart in the human adult. Now the human heart 

 contracts, in a condition of health, at least from 72 to 78 times in a 

 minute, (according to Gruy, Volkraanu, &c.,) whence it follows, 

 assuming the lowest figure, 120 grammes and 72 pulsations, in order 

 to be rather under the mean than to take numbers that might be 

 thought too high, that (72 x 120) 8640 grammes of blood are ex- 

 pelled from the left ventricle every minute. In one hour (60 X 8640) 

 518,400 grammes, and in twenty-four hours (518,400 x 24) 12,441,600 

 grammes, or in round numbers, 12,440 kilogrammes (1000 kilo- 

 grammes are nearly equal to an English ton). 



Of these 12,440 kilogrammes of blood leaving the left ventricle in 

 the course of one day, how much passes through the liver and the 

 kidneys ? It is impossible to say what this quantity may be exactly, 

 but an approximation may he arrived at sufficiently near the truth 

 for the purposes of our enquiry. According to Ferneley, Paget, 

 Valentin, and Volkmann, the sum of the sectional areas of the 

 branches of an arterial trunk is somewhat greater than the sectional 

 area of the trunk itself. 



In reference to the aorta, Paget, adopting the mean of twelve 

 measurements, gives the following proportions : — 



The area of a section of the aorta where it emerges from the peri- 

 cardium, is to the sum of the sectional areas of the three first large 

 branches, and of its thoracic branch, as 1 is to 1.055. Disregarding 

 this slight difference, it may be said from what is known at the pre- 

 sent day, that the quantity of blood which flows in a given time, 

 through a large arterial branch, is (nearly) to the quantity of blood 

 which flows through the aorta before it gives off its first branches, 

 as the sectional area of this large branch is to the sectional area of 

 that part of the aorta. Again, the areas of circles being to one 

 another as the squares of their diameters, if the diameter of an 

 artery arising from the aorta, and also the diameter of the aorta 

 before giving off its first branches be known, the quantity of blood 

 flowing through the artery in the course of one day can be readily 

 determined. The diameter of the human aorta at its origin (accord- 

 ing to Paget, Valentin, and myself), is about 28 millimetres, the 

 square of which is 784 ; hence the quantity of blood which flows 

 through the aorta at its origin, and which amounts to, at least, 

 12,300 kilogrammes, is to the quantity of blood flowing through the 



