QUANTITY OF BLOOD. 343 



produced by a tryptic enzyme which originates from the leucocytes 

 as well as by traces of a peptic enzyme. A chemical analysis of leucaemic 

 blood has been made by ERBEN. 1 



A great number of investigations have been made on the chemical 

 composition of blood in disease. But as we have only a few analyses 

 of the blood of healthy individuals, and as the possible variations under 

 physiological conditions are little known, it is difficult to draw any pos- 

 itive conclusions from the analyses of pathological blood. Unfortunately, 

 on account of the large number of contradictory deductions concern- 

 ing the composition of the blood of diseased human beings, it is impossible 

 to give a brief summary of the results, still the changes in the blood in 

 disease must be of the greatest importance. 



The quantity of blood is indeed somewhat variable in different species 

 of animals and in different conditions of the body; in general we consider 

 the entire quantity of blood in adults as about ArA of the weight of the 

 body, and in new-born infants about yV- HALDANE and LORRAIN SMITH, 2 

 who have determined the quantity of blood by a new method, find in 

 fourteen persons that it varies between -^ and ^ of the weight of the body. 

 According to the same method OERUM S has determined the quantity 

 of blood in men as about iV an d in woman -fa of the weight of the body. 

 Fat individuals are relatively poorer in blood than lean ones. During 

 inanition the quantity of blood decreases less quickly than the weight 

 of the body (PANUM 4 ) , and it may therefore be also proportionally greater 

 in starving individuals than in well-fed ones. 



By careful bleeding, the quantity of blood may be considerably dimin- 

 ished without any dangerous symptoms. A loss of blood amounting 

 to one-fourth of the normal quantity has as a sequence no lasting sink- 

 ing of the blood-pressure in the arteries, because the smaller arteries 

 accommodate themselves to the small quantities of blood by contract- 

 ing (WORM MULLER 5 ) . A loss of blood amounting to one-third of 

 the quantity reduces the blood-pressure considerably, and a loss of 

 one-half of the blood in adults is dangerous to life. The more rapid the 

 bleeding the more dangerous it is. New-born infants are very sensitive 

 to loss of blood, and likewise fat, old, and weak persons cannot stand 

 much loss of blood. Women can stand loss of blood better than men. 



The quantity of blood may be considerably increased by the injection 

 of blood from the same species of animal (PANUM, LANDOIS, WORM 



iZeitschr. f. klin. Med., 66 (1908). 



2 Journ. of Physiol., 25. 



3 Deutsch. Arch. f. klin. Med., 93 (1908). 



4 Virchow's Arch., 29. 



6 Transfusion und Plethora, Christiania, 1875. 



