216 THE STRUGGLE FOR LIFE. 
passes through certain glands, called lymphatic glands, in 
them, no doubt, its injurious properties are modified, and 
these glands also act as filters to arrest the passage of 
harmful solid particles into the blood. It is a well-known 
fact, that the glands, through which the lymphatics coming 
from tuberculous or cancerous tissues pass, do arrest, at all 
events for a time, the tubercle Bacilli and cancer cells, and 
stop their further progress towards infecting new parts. 
I have only to add, that the lymphatics of the intestine 
are called Lacteals, and that it is through them that the 
fat contained in the food is chiefly absorbed for the nutri- 
tion of the body. 
I am now in a position to speak of that wonderful fluid, 
the blood. I shall however, not describe its chemical com- 
position, but only the characters it presents to the eye 
when seen through the microscope. 
If I prick my finger, draw a small drop of blood, and 
compress it between a glass slide and a cover glass, you 
will see that the apparently red and fluid blood consists of 
three distinct elements. There will be seen a great num- 
ber of yellowish disks, the red blood corpuscles; a few 
granular bodies, the white blood cells; and these are floating 
in a clear fluid. These three elements are very distinct in 
nature and use, and I must say a few words about each 
of them. 
Firstly, about the fluid or blood plasma. _ This, so long 
as it is contained in healthy vessels, is fluid, but contact 
with the wall of a diseased vessel, or with a foreign body, 
or even with the air, causes it to solidify or coagulate, and 
it also coagulates after death. It is to this property that 
the arrest of hemorrhage is due, for if the blood remained 
fluid after a vessel was damaged, the smallest wound might 
cause fatal bleeding. After coagulation, the plasma sep- 
arates into two portions, one fluid, called serum, and the 
other more solid, called fibrine. The fibrine, during the 
