CHAPTER XI 



DISTURBANCES OF CIRCULATION AND DISEASES 

 OF THE BLOOD 



THE COMPOSITION OF THE BLOOD 



THE function of the blood being to maintain an equilibrium 

 in the temperature, chemical composition and osmotic pressure 

 between all parts of the body, it follows that it is never of 

 exactly the same composition in any two places or at any two 

 times. To the extent that every tissue is continually giving 

 off something to the blood, we may consider that every organ 

 is a factor in its formation, and as a result of this multiplex 

 origin of the blood, the substances it may contain are beyond 

 enumeration. There are probably but few chemical substances 

 occurring in the tissue-cells that do not also occur in greater or 

 less amount in the blood. In addition to these there are also 

 the substances characteristic of the blood itself, besides a host 

 of substances of unknown nature, apparently manufactured in 

 response to the stimulation of substances entering the body from 

 outside ; for we find that the blood of every adult individual 

 contains substances that make him immune to a multitude of 

 diseases that he has had in childhood, as well as substances 

 that in later life protect him to a greater or less degree from 

 infection by such organisms as the colon bacilli of his intestine, 

 the pneumococci and streptococci in his throat, etc. We have 

 learned of these defensive substances within very recent times, 

 and also of the " antienzymes " that possibly protect the blood 

 from the digestive enzymes of the body cells. What other 

 substances of importance we may yet find in the blood is 

 an open question. There are no apparent limits to the 

 possibilities of the study of the blood, for it represents a 

 little of every organ, and a good deal that is characteristic of 

 itself. 



In discussing briefly the substances that have been isolated 

 from the normal blood, before considering the changes that 

 occur in it during pathological conditions, we may roughly 

 divide the blood into the formed elements and the plasma in 

 which they are suspended. 



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