CHAP. III.] THE BLOOD IN DISEASE. 149 



metres). The corpuscle whose diameter is only 7yn has the volume 

 of 57/z.c.c. ; that of 6'5yLt has a volume of 49/>tc.c. 



When in anaemia the mean diameter of the blood-corpuscles falls 

 to 7/A, 100 corpuscles correspond in volume to only 80 healthy 

 corpuscles ; when the mean diameter falls to 6/4, 100 corpuscles 

 correspond only to 65 healthy corpuscles. 



Even assuming that the proportion of haemoglobin remained 

 constant in anaemia, it is obvious from the above considerations, 

 that important consequences must result from the diminution in 

 the size of the corpuscles, but as will be shewn subsequently, the 

 proportion of haemoglobin does not remain normal. 



2. Number. Usually the number of the coloured corpuscles is 

 diminished in anaemia, but by no means constantly so. In the most 

 intense cases of anaemia the diminution is however always very 

 marked. In a case of malarial anaemia Hay em found 1,182,750 

 corpuscles in 1 cubic millimetre, and in a case of purpura hemorrhagica 

 only 1,000,000, i.e. a diminution of the blood-corpuscles to between 

 Jth and <Uh the normal amount. 



3. Form. The corpuscles of anaemic blood assume modifications 

 of shape which would seem to depend upon a diminished consistence, 

 and which affect chiefly the medium-sized or small corpuscles, which 

 often assume an elongated oval form. 



4. Colour. The most important character which distinguishes 

 the blood of anaemia from healthy blood is a comparatively pale colour 

 of its red corpuscles, which depends directly upon a diminution in the 

 amount of haemoglobin. If by 1 we represent the maximum amour t 

 of haemoglobin, as measured by its colorific intensity, present in the 

 unit volume of healthy blood, we shall find that the amount may be 

 as low as 0'85 without health being sensibly impaired; indeed the 

 unit volume of blood of mean composition contains a quantity of 

 haemoglobin which fluctuates between 0'85 and 0'90, as compared 

 with 1 (the maximum amount of haemoglobin contained in healthy 

 blood). In anaemia, the amount of haemoglobin diminishes so much 

 that the amount present in the unit volume may be represented by 

 fractions varying between the limits 0'66 and 0'125, so that in the 

 most intense anaemia the quantity of haemoglobin may sink to one- 

 eighth its normal amount. In cases of anaemia of moderate intensity 

 the amount varies between one-half and one-fourth. 



We have seen that most interesting conclusions may be drawn 

 from a consideration of the size alone of the corpuscles in anaemia; 

 still more interesting are, however, the results of simultaneous enume- 

 ration of the corpuscles and determination of their colorific intensity. 



Thus if we find the number of corpuscles in a cubic millimetre of 

 blood to be 4 millions and the colorific intensity to correspond only 

 to that of 2 million healthy corpuscles, we at once come to the 

 legitimate conclusion that, in respect to the amount of haemoglobin 

 which it contains, each corpuscle, in the case under investigation, is 

 equivalent to one-half a healthy corpuscle. 



