152 PHYSIOLOGY CHAP. 



VIII. In order to appreciate the importance of the functions 

 of the blood in the animal economy, it will he well to examine 

 briefly the most important consequences of haemorrhage and 

 transfusion of blood. 



(a) Loss of blood, however produced, results in a weakening of 

 the body in correspondence with the amount of blood lost. A 

 haemorrhage of 30 grms. is dangerous or deadly in the new-born 

 infant, of 180-200 grms. in a child of one year old, of half the blood 

 (2000-2500 grms.) in the adult. Women appear to stand loss of 

 blood relatively better than men, because they have the power, 

 being subject to periodical haemorrhages (menstruation), of reform- 

 ing it more quickly. In consequence of the relative speed at 

 which blood forms again it is possible to obtain a greater volume 

 of blood by repeated bleeding than was originally present in the 

 animal, without causing its death. 



Vierordt (1854) was one of the first to investigate the effect of 

 bleeding upon the number of red corpuscles, and he found that 

 they diminished continuously with successive bleeding, and that 

 death occurred when the relative quantity of blood corpuscles 

 fell below a certain limit, which differs for different individuals. 

 If the loss of blood is not pushed so far as to kill the animal there 

 will be an increased influx of lymph into the blood, by which more 

 water, with its contained salts and proteins, is taken up from the 

 tissues. The neo-forrnation of erythrocytes takes longer. A con- 

 dition of hydraemia then obtains, associated with oligocythacmia 

 and leucocytosis, due to the increased passage into the blood of lymph 

 which carries a greater number of leucocytes with it. All these 

 facts (and others which we shall discuss in speaking of haemato- 

 poiesis) have been substantially confirmed by recent observers 

 (Hayem, Bizzozero, Golgi). 



(&) The effects of transfusion of blood are more important. We 

 must distinguish between direct transfusion, from vein to vein, 

 and indirect, viz. the injection of extracted and defibrinated blood, 

 between homogeneous transfusion of the blood of the same species 

 and heterogeneous transfusion of the blood of animals of other 



O 



species. 



Direct homogeneous transfusion is readily tolerated. According 

 to the observations of Worm-Miiller the normal quantity of serum 

 in an animal can be increased to 83 per cent, in consequence of 

 the great adaptability of the vascular system, without serious 

 symptoms. But if the increase of blood is carried too far, so that 

 its quantity is doubled, alarming symptoms occur, and when the 

 increase is raised to 145 per cent the animal dies from interstitial 

 haemorrhage, in consequence of vascular laceration. 



If a certain quantity of blood is transfused, there will be a 

 rapid return to the normal, owing to increased elimination from 

 the kidneys. The proteins of the plasma are also reduced (if less 



