632 VIS MEDICATRIX NATURAE 



was a seedling in 271 B.C., suffered a burn three feet wide 

 when it was 516 years old, and spent 105 years in folding 

 its living tissues over the wound. When it was killed at 

 the age of 2,171 years, a Methuselah among trees, it was 

 engaged in healing a third great wound 18 feet wide and 

 about 30 feet high. Vis medicatrix Natures. 



A sponge can be cut up and planted out like a piece of 

 potato-tuber; it may be minced and pressed through a cloth 

 sieve without losing its power of regrowth. An earthworm 

 thinks nothing of regrowing a new head or a new tail, or a 

 snail its horn and the eye at the tip, even unto forty times. 

 And this regenerative capacity is in the main adaptive in 

 its distribution, for, as Lessona and Weismann have shown, 

 it tends to occur in those animals and in those parts of 

 animals which are in the natural conditions of their life 

 peculiarly liable to non-fatal injury. Long-legged and lanky 

 animals like crabs and starfishes usually show much of it; a 

 self-contained globular animal like a sea-urchin shows little. 

 The chameleon is one of the few lizards that does not regrow 

 a lost tail, for, as it keeps it safely coiled around the branch, 

 the regenerative capacity has fallen into abeyance. 



Many other instances might be given of Nature's healing 

 power: the processes of rejuvenescence which in many or- 

 ganisms are continually at work in staving off senescence; 

 the natural defences of organisms, such as the bodyguard of 

 migratory phagocytes which deal with intruding microbes, 

 and the mysterious intrinsic counter-actives or anti-bodies 

 which deal with toxins ; the immunity which some animals 

 have to poisons, as the mongoose to snake-bite ; the regulatory 

 processes which sometimes occur when development or nor- 

 mal function is disturbed ; the absence of disease and senility 

 in wild life; the way in which some simple animals evade 



