THE STRUGGLE FOR LIFE. 21g 
starvation, partial or complete. On the other hand, if the 
refuse be insufficiently removed, the whole body will be 
poisoned in a corresponding degree. 
I will now briefly describe some of the ways in which 
the various elements of the blood assist in the struggle for 
life, and also some of the means by which the body is 
defended from its enemies, domestic and foreign. The re- 
searches of the past few years have fundamentally altered 
all our conceptions of these processes, and bid fair to furnish 
us with new and powerful weapons, and new defensive 
armour, to aid us in our struggle against disease and death, 
or rather against death from certain diseases. And yet, 
as is generally the case, when a striking advance of know- 
ledge is made, there have been premonitions of the truth, 
but these have not been understood, or have been merely 
looked upon as isolated facts, instead of as examples of a 
general law. More than a century ago, Edward Jenner, a 
country Surgeon, showed that by means of Vaccination, 
Small-pox, that most loathsome scourge of communities, 
could be robbed of nearly all its terrors. No one now 
living can realise the horrors of Small-pox, how it destroyed 
its thousands, and what wrecks it often made of the sur- 
vivors, leaving them blind and in other ways _ helpless 
members of Society. 
The two elements of the blood known to participate in 
the struggle against injurious matter are the serum and the 
white cells, their modes of action, however, are of very 
different natures. But, before I begin to describe the way 
in which they act, I have one other statement to make, 
which is this, that the white cells of the blood are scarcely 
distinguishable from the nuclei of the connective tissue 
cells, that is, the tissue which binds together the various 
organs of the body. These nuclei probably possess similar 
powers, and they are both capable of acting in the same 
way as I lately described the Amcba as doing when 
