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The special point to which I wish to draw your attention 

 this evening is that of " abnormal variations in the corpuscular 

 elements of the blood." 



It is one that, perhaps, interests me more than some 

 others, because these variations, which are constantly taking 

 place, have often very great significance, and, from a careful 

 observation of them, one is frequently enabled to draw 

 inferences of great value, both in diagnosis and also in the 

 treatment of disease. 



The blood, as we know, is a tissue whose constitution is 

 constantly fluctuating and changing, not only in its corpuscular 

 elements but also in its every constituent. 



I propose, first, to describe the normal corpuscular 

 elements of the blood, and then to refer to some of the more 

 marked variations. 



There are two large classes of corpuscules, the red and 

 the white. 



The red are to be counted by billions, 5,000,000 being 

 found normally to the cubic millimetre. Each corpuscle 

 appears in a specimen of fresh normal blood as a " homo- 

 geneous biconcave disc-shaped body, with opaque, yellowish 

 rim and nearly transparent centre." 



They are elastic, and capable of being folded and indented 

 without rupture. After infancy they are invariably non- 

 nucleated. 



Their usual size is 7'5 micro millimetre, and in fresh 

 specimens tend to form rouleaux. 



Each cell contains a substance called haemoglobin, which 

 has the power of combining loosely with oxygen, and acts as 

 an oxygen carrier to the tissues. 



The variations to which the red cells are liable are : — 



1. A change in the relative amount of haemoglobin, 



2. A change in shape — poikilocytosis. 



3. The appearance of nuclei. Normoblasts — 

 signifying an attempt at rapid new formation, 

 megoloblasts — signifying degeneration. 



4. Variation in number. 



