THE TOTAL QUANTITY AND DISTRIBUTION OF THE BLOOD 229 



much larger quantity, because the production of a secretion or excre- 

 tion always presupposes an abundant supply of fresh material. It 

 should also be noted that an organ may receive a large amount of 

 blood at any given time but may not retain much of it. Again, it 

 may receive only a small quantity of blood, but hold a considerable 

 portion of it in reserve as "residual blood." To illustrate: The in- 

 testine of a dog of medium weight is supplied with about 2.5 c.c. of 

 blood in a second, or 150 c.c. in a minute. While this amount may 

 seem to be unusually large, it should be remembered that the intestine 

 of an animal of this kind weighs about 500 grams, so that the 150 c.c. 

 of blood must actually be distributed to 500 grams of tissue substance. 

 Hence, as only about 30 c.c. of blood are allotted to each 100 grams of 

 intestine in a minute, this organ cannot be said to be very vascular. 

 The reverse relationship exists in the case of the kidney. While the 

 blood-supply of this organ is as copious as that of the intestine, its 

 vascularity must be much greater, because its average weight is only 

 40 to 50 grams. In the succeeding table 1 the different organs of the 

 dog have been arranged in accordance with the amounts of blood re- 

 ceived by them per 100 grams of substance and per minute. 



5 c.c. for the post, extremity 58 c.-c. for the spleen 



12 c.c. for the skeletal muscle 59 c.c. for the liver (venous) 



20 c.c. for the head 84 c.c. for the liver (total supply) 



21 c.c. for the stomach 136 c.c. for the brain 

 25 c.c. for the liver (arterial) 150 c.c. for the kidney 



30 c.c. for the portal organs, com- 480 c.c. for the suprarenal body 



bined 560 c.c. for the thyroid gland 



31 c.c. for the intestine 



According to these results, the vascularity of the liver is surpassed 

 by that of the brain, kidney, adrenal body and thyroid gland. But if 

 considered solely from the standpoint of the blood-supply, the quantity 

 allotted to this organ must be larger than that of any other, because 

 as it receives about 7.0 c.c. in a second, its supply per minute amounts 

 to more than 400 c.c. It will be seen, therefore, that the blood must 

 complete the circuit through its channels once in about every three 

 minutes. In accordance with the analyses of the respiratory air by 

 Zuntz, 2 Krogh 3 and Boothby, 4 the lungs of man receive more than 3 

 liters of blood in a minute. 



The data presented by Ranke 5 tend to show that the blood is distri- 

 buted at any one time as follows: one-fourth to the heart, lungs and 

 central blood-vessels, one-fourth to the liver, one-fourth to the mus- 

 cles and one-fourth to the remaining organs. These values have been 

 obtained by measuring the amount of blood contained in the b ood- 



1 Compiled in accordance with data presented by Burton-Opitz in Pfliiger's 

 Archiv, cxxix, 1908, and Quarterly Jour, of Physiol., iv, 1911. 



2 Zeitschr. fur Balneologie, iv, 1912. 



3 Skand. Archiv fur Physiol., xxvii, 1912. 



4 Am. Jour, of Physiol., xxxvii, 1915. 



6 Die Blutverteilung und Thatigk. der Organe, Leipzig, 1871. 



