CHAPTER III 



THE APPLIED PHYSIOLOGY OF THE BLOOD AND 



H.EMOPOIETIC OEGANS 



GENERAL FUNCTIONS OF THE BLOOD. 



FROM the earliest times of medical science the blood has 

 attracted to itself the most earnest attention of the 

 investigators of the secrets of life. Whole systems of 

 pathology have been built up upon supposed alterations 

 in its properties, and have subsequently fallen into 

 disregard, and yet in these latter days there is still no 

 field of research which is cultivated with more en- 

 thusiasm. Nor is the reason for this far to seek. Blood 

 is the one constituent common to all the organs and 

 tissues alike. It is the currency or medium of exchange 

 in the body, giving to every cell the substances necessary 

 for its life, and receiving back from it again the products 

 of its activity or waste. In this respect the blood, as it 

 flows ceaselessly along the bloodvessels, has been aptly 

 compared to the water in the canals of such a city as 

 Venice or Amsterdam, which brings to the doors of the 

 inhabitants the provisions necessary for their life, and 

 carries away the products of their handicraft, but which 

 is at the same time the recipient of their refuse and 



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