66 PERSONAL APPEARANCES IN HEALTH AND DISEASE. 



puscle when viewed alone seems to have very little colour 

 at all, a mere faint tinge, and if a drop of water be added 

 to the blood the corpuscle will swell up and become glo- 

 bular, and its colour will become even fainter than before. 

 But, even under the microscope, it will be seen how the 

 corpuscles are sufficient to account for all the colour the 

 blood possesses, for the little bodies have a great tendency 

 to collect in groups, especially forming rows like a pile of 

 coins, and then the colour of the whole group is more 

 manifest. If further proof be needed that the colour of 

 the blood is due to these little particles, it may be found 

 by collecting a small quantity of blood and exposing it 

 to the air. After a short time the fluid will set it under- 

 goes what is called coagulation- the resulting solid mass 

 being called a clot. This clot is formed by the pro- 

 duction of a substance from the fluid part of the blood 

 known as fibrine, which does not exist as such in the 

 blood when circulating through the body. The fibrine 

 is formed in short and fine threads which entangle the 

 corpuscles in their meshes. Now the red corpuscles 

 being relatively heavier than the fluid part of the blood 

 sink to the bottom of the vessel during the process of 

 coagulation, and more of them will sink the slower this 

 process takes place. Hence it comes to pass that 

 whereas the lower part of a clot so formed is of a dark red 

 colour, the upper layers may be. almost colourless ot 



