FRANKLIN C. McLEAN 



in which edema was disappearing, this decrease amounting in one of the 

 cases to 510 c.c. This would indicate that although the ratio of plasma 

 volume to body weight remained unchanged during the time that edema 

 appeared, there was an increase in actual volume of plasma amounting 

 to about 30 per cent of the original volume. Bock's data would therefore 

 appear to confirm Krehl's suggestion of the possibility of "edema of the 

 blood" as a part of generalized edema. There is no evidence to the effect 

 that the increase in plasma volume precedes or is in any way responsible 

 for the occurrence of general edema. 



Composition of the Blood in Heart Failure. According to pres- 

 ent conceptions of the physico-chemical mechanism of the exchange of 

 fluid between the blood and tissues, it is important to inquire into the 

 changes in the composition of the blood in heart failure. It is not possible 

 to conclude, however, that such changes in its physico-chemical constitu- 

 tion as may be demonstrated are responsible for edema, for changes in the 

 tissues themselves may result in changes in the composition of the blood. 

 Changes in the blood are then the results of edema, rather than its 

 causative factors. Such changes as have been demonstrated are sum- 

 marized in the following paragraphs: 



OXYGEN CONTENT OF BLOOD IN HEART FAILURE. The oxygen content 

 of the blood, and particularly the degree of oxygen unsaturation of arterial 

 and venous blood in heart failure, have recently been studied by Lunds- 

 gaard(&) (d) and by Harrop(c). Lundsgaard found the oxygen unsatura- 

 tion of venous blood to be increased beyond the normal limits in all cases, 

 except in instances in which the symptoms of heart failure were rapidly 

 lessening. Ilarrop found in nine patients seven with an abnormally low 

 oxygen saturation in arterial blood, and four of these regained normal 

 values when the circulatory disturbances were relieved. The lowest value 

 for oxygen saturation found in these cases was 81.4 per cent, as compared 

 with the average value of 95.5 per cent, and a low value of 94.3 per cent 

 in fifteen normal individuals. 



CARBON DIOXID CONTENT OF BLOOD IN HEART FAILURE. Peters 

 found the content of carbon dioxid in the venous blood, when considered in 

 relation to the alveolar carbon dioxid tension, to be increased in heart fail- 

 ure. This condition was attributed by him to impaired aeration of the 

 blood in the lungs. Koranyi(a) (&) and his pupils have correspondingly 

 found an increased depression of the freezing point of the blood in heart 

 failure, which they have attributed to its increased carbon dioxid content, 

 since the freezing point could be restored to normal by driving off carbon 

 dioxid from the blood, and since their findings for the blood of patients 

 with heart failure could be duplicated on the blood of normal individuals, 

 if carbon dioxid were passed through the blood in vitro before the deter- 

 minations were made. 



