410 W. H. GASKELL. 



It is the mode of death of the red corpuscles which would 

 occur were the blood subjected to no other changes than those 

 involved in carrying on its respiratory functions. This change 

 can be best studied in extravasated blood. 



The chief evidence of passive destruction is the presence of 

 pigment, and in health the chief organs in which this evidence 

 is to be found are the spleen and bone marrow. The chief 

 characters of this pigment are the large and varying size of 

 the pigment particles and their irregular shape. The larger 

 the red corpuscles of the animal the larger are the pigment 

 particles which result from their passive destruction. He 

 attaches special importance to this difference in the character 

 of the pigment in the two varieties of blood destruction. From 

 it alone he is able to say in any particular case whether the 

 pigment has been formed in situ from red corpuscles, or from 

 free haemoglobin carried thither in solution. When once 

 formed this blood-pigment is remarkably resistent to the 

 action of reagents. It can be recognised long after the death 

 of the original blood-corpuscles. Hence the amount of pigment 

 found in the organs specified affords a most reliable indication 

 as to the amount of passive destruction that has occurred. 



Active destruction depends on certain changes in the blood, 

 most marked during digestion, and occurring chiefly within 

 the blood of the portal system. The spleen, however, is par 

 excellence the seat of active blood destruction. Active 

 destruction in this organ is specially favoured by certain struc- 

 tural features, viz. (1) slowness of circulation, (2) closeness of 

 relation of the cells of the pulp to the blood flowing through 

 it, (3) capacity for accommodating large and varying quantities 

 of blood. 



The same features favour also the seizure of red corpuscles 

 in process of becoming effete by slow and gradual decay. The 

 spleen is thus also the great seat of passive destruction, and is 

 hence the chief seat of pigment accumulation resulting from 

 this process. Next to the spleen the red bone marrow is the 

 most important seat of passive destruction, the structural 

 features here being closely similar to those in the spleen. 



