4 ANIMAL LIFE 



earthworms under the influence of special rays of 

 light that the treatment known by Finsen's name 

 owes its origin. 



Finsen noticed that when the prismatic colours 

 of sunlight are successively cast on the worm, the 

 blue and violet rays — and they alone — cause irritation 

 and distress. Accordingly, he began a systematic 

 work on the different effects which coloured light 

 exerted in virtue of its properties on healthy and 

 diseased skin, and the beneficial effects of his dis- 

 covery are now restoring to health and activity every 

 year hundreds who but for this work on worms would 

 have received no effective assistance. But the earth- 

 worm is far more than the corpus vile of a successful 

 experiment. It is the unseen agriculturist, bringing 

 the subsoil to the surface for light, air, and rain to 

 vivify and replenish. It is the preserver of ancient 

 monuments, protecting them by an encasement of earth 

 from destruction. More significant still, it is one of 

 a tribe whose ancestors have had a great share in the 

 origin of higher forms of life. The links that bind 

 together the crab and lobster — the Crustacea — the 

 insects, and probably even the vertebrate animals, 

 find their common starting-point in the lowly worm, 

 and as we trace back some natural characteristics of 

 our race to an obscure tribe, such as the Frisian, so does 

 the naturalist trace the hidden peculiarities of the 

 structure of the higher animals to the worm, in which 

 those features are more manifest. 



Perhaps the most unexpected results of this historic 



