CHAPTER I. 



THE BLOOD AND THE BLOOD-FORMING ORGANS. 1 



Changes in the Composition and Structure of 

 the Blood. 



The Coagulability of the Blood and the characters of the resulting 

 clot vary widely, depending partly upon the composition of the blood and 

 partly upon the conditions under which the coagulation occurs. There 

 may be very little coagulation of the blood in death from suffocatioji^or 

 from conditions which interfere with the aeration of the blood and per- 

 mit the accumulation of carbonic acid within it. Thus, in death from 

 strangulation or drowning, many chronic diseases, scurvy, and under 

 many conditions which we do not understand, the blood may remain 

 fluid, or nearly so, after death. On the other hand, in a variety of in- 

 fectious diseases, such as rheumatism, pneumonia, etc., very voluminous 

 clots may be formed, although this is by no means constantly the case. 

 The fact that large clots form after death is not conclusive evidence that 

 an undue amount of fibrin-forming elements was present in the blood, 

 nor does the absence of marked coagulation prove a diminution in the 

 blood of fibrin-forming elements. 



The composition of the clot varies with the rapidity of its formation 

 and with the specific gravity of the plasma. Clots very rapidly formed 

 in plasma of high specific gravity, or in still slowly circulating blood, 

 are apt to be dark red, from admixture of red cells and fibrin. After 

 complete failure of circulation, especially in plasma of low specific grav- 

 ity, the red cells tend to settle to dependent vessels. Yellowish-white 

 succulent clots then form in the clear supernatant plasma, while soft 

 black clots result from the excess of red cells collected in the dependent 

 vessels. From a clinical point of view it is important to note that in 

 jaundice_the coagulability of the blood is greatly reduced. 



The Alkalinity of the Blood. This varies in health and to a greater 

 extent in disease, this variation being parallel with the fluctuations in con- 

 centration and albumen content. Diminution in the alkalinity of the 

 blood is seen in severe anaemia and in diabetes. Increase has been noted 

 in catarrhal jaundice. In fever the variations are marked; they may 

 be above or below normal, but a constant change has not been observed. 



Anhydrsemia the condition in which the blood contains an excessive 

 proportion of albumen, cells, and other solid elements occurs in dis- 

 eases associated with excessive serous discharges from the intestines. It 

 is extreme in some cases of cholera, and has been noted in a lesser degree 

 in other infectious diseases, asjmeumouia and diphtheria. 



1 A full discussion of the subjects in this chapter can be found in Ewing, "Clinical 

 Pathology of the Blood," 1903. 



