426 BLOOD AND LYMPH. 



second and third days. This latter phenomenon constitutes what 

 is known as the posthemorrhagic fall.* 



Blood-transfusion. Shortly after the discovery of the circu- 

 lation of the blood (Harvey, 1628), the operation was introduced 

 of transfusing blood from one individual to another or from some 

 of the lower animals to man. Extravagant hopes were held as to 

 the value of such transfusion not only as a means of replacing the 

 blood lost by hemorrhage, but also as a cure for various infirmities 

 and diseases. Then and subsequently fatal as well as successful 

 results followed the operation. It is now known to be a dangerous 

 undertaking, mainly for two reasons: first, the strange blood, 

 whether transfused directly or after defibrination, is liable to contain 

 a quantity of fibrin ferment sufficient, perhaps, to cause intravas- 

 cular clotting ; secondly, the serum of one animal may be toxic 

 to another or cause a destruction of its blood corpuscles. Owing to 

 this hemolytic and toxic action, which has previously been referred 

 to (p. 387), the injection of foreign blood is likely to be directly 

 injurious instead of beneficial. In cases of loss of blood from severe 

 hemorrhage, therefore, it is far safer to inject a neutral liquid, 

 such as the so-called "physiological salt solution" a solution of 

 sodium chlorid of such a strength (0.7 to 0.9) as will suffice to pre- 

 vent hemolysis of the red corpuscles. 



*Dawson, "American Journal of Physiology," 4, 1, 1900. 



