128 GLIMPSES OF NATURE. 



an independent animalcule. This power of feeding, 

 we shall see, is an important characteristic of our 

 wandering particle. 



On this account it has been called a " phagocyte " 

 literally an " eating-cell." In all ordinary animals, from 

 man downwards, then, we see these white blood-cells, 

 migrating from blood-vessels, passing out among the 

 tissues, and thus showing forth an independence which 

 is not without physiological reason or justifiable pre- 

 text. The further story of their life-work is interest- 

 ing and may be readily understood. For it is now a 

 matter of certainty that among all the servants of our 

 bodies, we possess none more active, none more faith- 

 ful, and none more necessary than our wandering cells. 



When the young frog or tadpole attains a certain 

 stage of development, and when it is about to exchange 

 its water-life for the higher land-existence, the fish- 

 like tail requires repression and demands extinction as 

 part and parcel of frog-advance. Of old, we believed 

 the disappearance of the frog's tail was due to a simple 

 process of atrophy or wasting away. We know better 

 to-day. 



By close microscopic investigation, we are able 

 to see a curious work proceeding in the tadpole's 

 appendage. It swarms with white cells which have 

 migrated into its substance from the blood-vessels. 

 They are there for a purpose, and they work with a 

 will. They are seen in the act of eating and devour- 

 ing the substance of their possessor. The tadpole in 

 this sense, and through its semi-independent white- 

 blood cells, is living upon itself, and eating up life's 

 " principal " in place of living upon the interest repre- 

 sented by its food. 



Within the bodies of these white cells in the tad- 



