CHAPTER XIII 



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 con- 

 tain 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 re- 

 sponse to the stimulation of substances entering the body from out- 

 side; 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 possi- 

 bly 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 

 much 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. 



THE FORMED ELEMENTS.— By weight, tlie red corpiu«clos constitvito from 

 40 to 50 por cent, of tli(> l)l()0(l, tlie i)crccnt:i}i;c varyinji; uiiiUn- (lilTc-ront conditions, 

 while llie total weif^ht of the leucocytes and platelets is insi<;iuticant. 'I'he henio- 

 fr|ol)in constitutes troni Sti to 94 i)er cent, by \veit;;ht of tiie solids of the red cor- 

 puscles, but the i)liysical and chemical relations that it bears lo the stroma of the 

 corpuscles are as yet undetermined (see "Hemolysis"). t)f tlie remaining constit- 



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