968 PHYSIOLOGY 



the serum. Thus in one experiment 100 grm. of defibrinated pigs' 

 blood contained 18-90 grm. protein plus haemoglobin. The blood- 

 corpuscles of 100 grm. of the same blood contained 15-07 grm. pro- 

 teins plus haemoglobin ; therefore the serum of the same 100 grm. of 

 blood contained 18-9015-07 = 3-83 grm. proteins. One hundred 

 grammes of serum contain 6-77 grm. protein. From these figures the 

 amount of serum in the 100 grm. of defibrinated blood may be com- 

 puted as follows : 



O.QQ 



. 100 = 56-6 per cent, serum. 



6-77 



10056-6 = 43-4 per cent, blood-corpuscles. 



The average volume of corpuscles in human blood can be taken as 

 50 per cent, of the total amount, different estimations having given 

 figures varying from 48 to 54 per cent. In the horse the volume of 

 corpuscles is 53 per cent., in the dog 36 per cent. 



THE ENUMERATION OF THE CORPUSCLES 

 In order to enumerate the red corpuscles the blood is diluted with 

 a known amount of an isotonic fluid and the number is counted in a 

 measured volume of the mixture. The average number of red cor- 

 puscles is about 5,000,000 per cubic millimetre in adult men and rather 

 fewer, about 4,500,000, in adult women. The enumeration of cor- 

 puscles is subject to considerable errors, probably not less than 10 per 

 cent. Moreover different conditions of the circulation may cause 

 variations in the relative distribution of plasma and corpuscles 

 respectively in different parts of the circulation, so that the blood- count 

 of a specimen from the capillaries of the finger or lobe of the ear may 

 vary considerably from a similar count of the corpuscles in blood 

 obtained directly from a minute vein or artery. More important 

 therefore is the determination of the haemoglobin. For this purpose 

 a measured quantity of the blood, 2 to 5 c.mm., is obtained in a 

 capillary pipette and mixed with a given volume of water. The red 

 fluid thus obtained is compared with a standard. This latter in von 

 Fleischl's instrument is a prism of coloured glass. In Oliver's 

 instrument the standard consists of a series of tinted glasses, one of 

 which represents the colour of a measured quantity of normal blood 

 diluted with water and placed in a flat glass cell of a certain size, while 

 the others represent percentages of haemoglobin below and above the 

 normal. The most accurate method is that due to Hoppe-Seyler and 

 Haldane, namely, the conversion of the blood sample into CO-haemo- 

 globin'and its comparison with a standard specimen of CO-haemoglobin, 

 which is stable in solution and can therefore be kept in a sealed glass 

 vessel for any length of time. 



