ilbS BLOOD AND LYMPH. 



of a severe hemorrhage (4.3 per cent, of the body-weight) followed 

 by transfusion of an equal volume of physiological saline. So far 

 as the red corpuscles and the amount of hemoglobin are concerned, 

 it will be noticed that the large sudden fall from the hemorrhage, 

 first day, is followed by a slower drop in both factors during the 

 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. So far as the use of the blood of 

 another animal is concerned, it is now known to be a dangerous 

 undertaking, mainly because 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. 422), the injection of foreign blood is hkely to 

 be directly injurious instead of beneficial. In human surgery 

 modern technic (Carrel) has overcome some of the difficulties 

 formerly encounterd in the transfusion of blood from one human 

 being to another. Anastomoses may be made between the blood- 

 vessels of the "donor" and the "recipient," so that the blood passes 

 from one to the other without coming into contact with a foreign 

 surface and, therefore, without danger of coagulation or the for- 

 mation of thrombin. Other simpler methods are used success- 

 fully for the same purpose. For example, the blood may be taken 

 from the vein of a "donor" with a syringe, coagulation being pre- 

 vented by the use of a proper amount of sodium citrate solution. 

 This citrated blood is then introduced directly into a vein, of the 

 "recipient." Such methods of transfusion are used very frequently 

 at the present time and often with good results. In cases of loss 

 of blood from severe hemorrhage it is simpler to inject a neutral 

 liquid, such as the so-called "physiological salt solution"- — a solu- 

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

 to prevent hemolysis of the red corpuscles. This method, how- 

 ever, has the disadvantages that its good effects are temporary. 

 The new fluid introduced into the circulation soon escapes into the 

 tissues, rendering the latter edematous. We may explain this fact 

 on the assumption that the filtration from the vessels into the 

 tissues is not compensated by an absorption of water from the 

 tissues into the blood. This latter act depends largely on the low 

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



