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 con- 

 tain are beyond enumeration. There are probably but few chemical 

 substances occurring in. the tissue-cells that do not also occur iii 

 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. 

 Wliat 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 weijjht, tlie red corpiisclos constitute from 40 

 to 50 per cent, of tlie l)lo(id, the percentage varying under difl'erent conditions, 

 while the total weight of tlie leucocytes and platelets is insignificant. The hemo- 

 globin constitutes from Sii to 04 per cent, liy weight of tlie solids of the red cor- 

 puscles, but the physical and chemical relations that it bears to the stroma of the 

 corpuscles are as yet undetermined (see ''Hemolysis"). Of tlie remainin£r constit- 

 uents of the corpuscles, from .5 to 12 per cent, consist of proteins, probably chiefly 

 globulins and nucleoproteins; 0.3 to 0.7 per cent, of lecithin; and about 0.2 to 0.3 

 19 289 



