BLOOD AND HyEMOPOIETIC ORGANS 75 



allow the passage outwards of haemoglobin, and this is 

 probably how blood pigment gets into the plasma in 

 cases of Baynaud's disease. Haemolysins also affect in 

 some way the permeability of the envelope without 

 necessarily dissolving the corpuscle. 



The red cells are also fairly rich in salts of potash, a 

 recognition of which fact, indeed, has led some people to 

 recommend the treatment of pernicious anaemia by the 

 administration of potassium compounds.* 



Practically, then, one may regard a red corpuscle as 

 an elastic bag designed for the transportation of haemo- 

 globin, and whether it be really ' alive ' or not is an 

 academic question still open to discussion. 



The red cells make up by far the larger proportion of 

 the population of the blood -stream, amounting on an 

 average to 5,000,000 per cubic millimetre of blood. In 

 women, and in the earlier years of life in both sexes, the 

 number is somewhat below this. On the other hand, in 

 some ' full-blooded ' individuals higher counts may be 

 obtained. The actual number of red cells and the 

 amount of haemoglobin in the blood apparently depend, 

 to a great extent, on the degree of muscular activity of 

 the body. In other words, the number of oxygen-carriers 

 is in proportion to the amount of oxygen needed. The 

 chief physiological condition which influences the number 

 of the corpuscles, however, is altitude, for numerous 

 observations have shown that with increasing elevation 

 above the sea -level the number of the red cells is 

 augmented, every 330 feet ascended causing an increase 

 of about 100,000 per cubic millimetre. The cause of 

 * Kumpf, B&rlm. KUn. Woch., 1901, xxxviii. 477. 



