TRANSACTIONS OF SECTION I. 675 
age blood volume actually increases as the animal grows heavier, while in the 
warm-blooded animals it undergoes a steady diminution. 
4. Other experiments, also carried out in association with Dr. Ray, have 
shown. that in mammals and birds a similar proportional relation to the body 
surface holds throughout each species examined both for the sectional area of the 
aorta where it leaves the heart and for that of the trachea just above its bifurca- 
tion. It has also been found that in passing from species to species the ratio of 
the weight of the heart muscle to the total oxygen capacity of the circulating 
blood is approximately constant in a number of different species of warm- 
blooded animals. 
5. As regards sex, it is found that the sectional area of the aorta is somewhat 
smaller, and the blood volume is smaller (about three per cent.) in the female than 
in the male animal of the same weight. During pregnancy, however, and in the 
puerperal state the blood volume of the female is considerably increased. 
6. Under normal conditions the blood volume of mammals is very delicately 
adjusted. If the blood volume be altered artificially by bleeding or by trans- 
fusion the process of adjustment begins so promptly that its effect is already 
recognisable in an alteration of the hemoglobin percentage when only a very 
small percentage of fluid has been removed or introduced, as the case may be. 
This fact has escaped consideration in many experiments; but it has an important 
bearing on conclusions drawn from observations upon hemorrhage and trans- 
fusion. 
7. The presence of excess of carbon dioxide in the air breathed quickly affects 
the volume of the blood, causing dilution of the plasma and an increase up to 
ten per cent. or more in the blood volume. This factor may be an important 
source of error in the interpretation of experiments carried out by respiratory 
methods. Amyl nitrite, which produces vascular dilatation, similarly leads to an 
immediate dilution of the plasma. 
8. The administration of chloral hydrate in quantities sufficient to produce 
anesthesia causes a rapid concentration of the plasma up to ten or fifteen per 
cent., and may thus lead to erroneous conclusions in experiments on the blood and 
respiration ; but ether anesthesia leaves the volume of the blood unaltered. 
2. A Contribution to the Study of the Effect of Altitude on the Blood. 
By Professor Georces Dreyer and Dr. HE. W. ArnuEY WALKER. 
1. In animals placed under novel conditions as regards altitude changes occur 
in the volume of the blood. These changes are of a regular character and follow 
a definite law. An analysis of the admirable series of observations on the blood 
volume of rabbits recorded by Abderhalden shows that the change of volume 
which occurs with a particular change of barometric pressure is proportional to 
the area of the body surface in different individuals of the given species. The 
blood volume of rabbits taken up from Basle (266 métres above sea-level) and 
kept at St. Moritz (1,856 metres above sea-level) still conforms to our formula 
0-72 
B= ay But & is now increased. That is to say, their blood volume is 
diminished by an amount exactly proportional to their body surface. 
2. At the altitude of St. Moritz the hemoglobin percentage shows an increase, 
and the number of red corpuscles per c.mm. undergoes a parallel increase. This 
change is at first entirely due to a rapidly occurring concentration of the blood. 
But later on it is also due in part to an increased formation of hemoglobin (and 
red corpuscles), raising the total oxygen capacity of the circulating blood. 
Abderhalden stated that there was no marked increase in the total hemo- 
globin. But he was probably misled by his method of calculation, since the in- 
crease can be shown quite clearly from his figures. This agrees with the conclu- 
sions of Zuntz, Loewy, Miiller, and Caspari. In their recent work Douglas, 
Haldane, Henderson, and Schneider state that at first the increase is due in part 
to concentration of the blood, but that the later increase is due entirely to the 
new formation of hemoglobin, and that the volume of the blood also becomes in- 
creased. This latter statement, that the blood volume is increased in man at high 
pie ga 
