SOME MICROSCOPIC FRIENDS. 129 



pole's tail, microscopists have been enabled actually to 

 see the fragments of muscle and nerve they have torn 

 from the tail substance. Little wonder that the tail 

 " grows small by degrees and beautifully less " under 

 such a vigorous attack ; and in the gills of the tadpole 

 (which disappear with the tail) the same devouring 

 process is seen to proceed. Thus, the disappearance 

 of the tail is a matter of vital action as much so, 

 indeed, in one sense, as its growth. It is a new 

 experience of life to find certain of the living particles 

 of the body set apart, as in the case of the frog, for 

 the work of ridding that body of its encumbrance, and 

 of assisting it to rise in the scale of life. 



Nor is this all. In the water-fleas w r hich swarm in 

 every brook, the white cells have been seen engaging 

 in a hand-to-hand fight with vegetable spores or fungi 

 which gained admittance to the bodies of the fleas, 

 and threatened to kill those animals. Like a ship 

 boarded by enemies, the water-flea's body was the 

 scene of a grim contest. As a writer puts it, if the 

 white cells overpower and eat up the vegetable in- 

 truders, the water-flea lives; if the cells fail to over- 

 come the invaders, the water-flea dies. 



A further thought about these microscopic friends 

 extends to human life. If our bodies receive germs 

 which grow and multiply within our tissues, what is 

 seen in the water-flea will occur within the human 

 frame. There is a battle between our white cells and 

 the germs of disease. If the latter are victorious, we 

 fall ill of the fever or other ailment ; if we escape 

 the fever, our immunity is due to the victory of our 

 microscopic friends over the germs. 



