THE AMOUNT OF BLOOD. 83 



some veins must be characterized by special peculiarities, such as the 

 blood from the portal vein and the hepatic veins. The essential differ- 

 ences between the two kinds of blood may be summarized as follows : 



ARTERIAL BLOOD CONTAINS 

 More Less 



Oxygen, water, fibrin, extractives, Carbon dioxid, blood-corpuscles, pro- 

 salts, at times chlorids, sugar, fat; teids, alkali, urea, 

 and the temperature is on an average 

 i C. higher. 



The bright red color of arterial blood is due to oxy hemoglobin, to 

 which it is peculiar; while the dark color of venous blood is due to a 

 deficiency in oxyhemoglobin and an abundance of reduced hemoglobin. 

 The larger amount of carbon dioxid in venous blood is not responsible 

 for the dark color, for if equal amounts of oxygen be added to two 

 portions of blood and to the one also carbon dioxid, the latter effects 

 no change in color. 



THE AMOUNT OF BLOOD. 



The amount of blood in the adult equals y 1 ^ of the body- weight, 

 in the newborn --$. 



According to A. Schiicking the amount of blood in the infant when the 

 umbilical vein is ligated immediately after birth is j^, while that in the infant 

 when ligation is practised later is as much as ^ of the body- weight. Immediate 

 ligation, therefore, causes a reduction of the amount of blood in the newborn 

 child of about 100 grams. Further, the number of red corpuscles is less in the 

 blood of the newborn child after immediate ligation than in that of infants in 

 which ligation is practised later. 



For the estimation of the amount of blood, first practised by Valen- 

 tine in 1838 and by Ed. Weber in 1850 by unreliable methods, the fol- 

 lowing may be employed : 



Welckefs Method. Blood from the incised carotid of a previously weighed 

 animal, with a cannula tied in the vessel, is received into a weighed flask, 

 in which it is defibrinated by agitation with pebbles. It is then measured. 

 A portion of the defibrinated blood is made cherry-red by the passage of carbon 

 monoxid, because ordinary blood possesses varying coloring power in accordance 

 with the amount of oxygen present. Now a \- shaped cannula is tied in both 

 extremities of the divided carotid and a 0.9 per cent, solution of sodium 

 chlorid is permitted to flow steadily from a pressure- vessel, while the resulting 

 wash- water that escapes from the divided jugular veins and the inferior 

 vena cava is collected until it becomes as clear as water. Then the entire 

 body is minced, and with the exception of the weighed contents of the 

 stomach and intestines, whose weight is deducted from that of the body, the 

 mass is extracted with water and expressed after the lapse of 24 hours. This 

 water and the sodium-chlorid wash- water are mixed and weighed. A portion of 

 this mixture is likewise saturated with carbon monoxid. Of this a specimen is 

 placed in a glass chamber with parallel walls, i cm. apart a so-called hema- 

 tinometer, while in a second chamber water is added to the undiluted blood 

 from a buret until both fluids exhibit the same shade of color. From the amount 

 of water that is necessary to make the dilution of the blood of the same tint as 

 the wash-water the amount of blood present in the latter can be estimated. In 

 mincing the muscles alone the coloring-matter yielded by them can be considered 

 as muscle-pigment and need not be taken into account. By multiplying the 

 volume of blood by its specific gravity the absolute weight of the blood can 

 be determined. As the differences in the color of the specimens can be esti- 

 mated most accuratelv this method is to be commended. 



