30 A MANUAL OF PHYSIOLOGY 



Enumeration of the Blood-corpuscles, This is done by 

 taking a measured quantity of blood, diluting it to a known 

 extent with a liquid which does not destroy the corpuscles, 

 and counting the number in a given volume of the diluted 

 blood (p. 61). 



The average number of red corpuscles in a cubic milli- 

 metre of blood is about 5,000,000 in a healthy man, and 

 about 4,500,000 in a healthy woman, but a variation of 

 1,000,000 up or down can hardly be considered abnormal. 

 In persons suffering from profound anaemia the number 

 may sink to 1.000,000 per cubic millimetre, or even less, 

 while in new-born children and in the inhabitants of high 

 plateaus or mountains it may rise to 8,000,000, or even 

 more. In the latter instance a residence of a fortnight in 



FIG. 3. CURVE SHOWING THE 

 NUMBER OF RED CORPUSCLES 

 AT DIFFERENT AGES (AFFER 

 SORENSEN'S ESTIMATIONS). 



The figures along the horizontal axis 

 are years of age, those along the 

 vertical axis millions of corpuscles 

 per cub. mm. of blood. 



the rarefied air is sufficient to bring about the increase, and 

 a subsequent residence of a fortnight in the lowlands to 

 annul it.* 



The number of white blood-corpuscles is on the average 

 about 10,000 per cubic millimetre of blood, or one leucocyte 

 for every 500 red blood -corpuscles. In leukaemia the 

 number of white corpuscles is enormously increased it may 

 be in extreme cases to 500,000 per cubic millimetre while 

 at the same time the number of the red corpuscles is 

 diminished ; and the ratio of white to red may approach 

 I : 4. An increase has also been observed in certain infec- 

 tive diseases as part of the inflammatory reaction. There 

 are also physiological variations, even within short periods 

 of time ; for example, the number of lymphocytes is in- 



* In 113 apparently healthy students (male) the average number of red 

 corpuscles was 5,190,000 per cubic millimetre. In 104 of these, the number 

 ranged from 4,000,000 to 6,400,000 ; in 71 (or 63 per cent, of the whole), 

 from 4,400,000 to 5,500,000 ; in 3, from 3,500,000 to 3,900,000 ; in 5, from 

 6,500,000 to 7,000,000. In one observation the number reached 7,300,000. 



