284 LAWS OF VAEIATION. Chap. XX J V. 



the limb was cut off, the deficient part, and no more, was exactly 

 reproduced. When a diseased bone has been removed, a new one 

 sometimes " gradually assumes the regular form, and all the attach- 

 " ments of muscles, ligaments, &c., become as complete as before."^ 



This power of re-growth does not, however, always act perfectly ; 

 the reproduced tail of a lizard differs in the form of the scales from 

 the normal tail : \vith certain Ortliopterons insects the large hind 

 legs are reproduced of smaller size:^ the white cicatrice which in 

 the higher animals ncites the edges of a deep wound is not formed 

 of perfect skin, for elastic tissue is not produced till long afterwards.^ 

 " The activity of the nisus formativiis," says Bhimenbach, " is in an 

 " inverse ratio to the age of the organised body." Its power is also 

 greater with animals, the lower they stand in the scale of organi- 

 sation ; and animals low in the scale correspond with the embryos of 

 higher animals belonging to the same class. Newport's observations ^ 

 afford a good illustration of this fact, for he found that " myriapods, 

 " whose highest development scarcely carries them beyond the larvae 

 " of perfect insects, can regenerate limbs and antennae np to the 

 " time of their last moult ;" and so can the larvae of true insects, 

 but, except in one order, not in the mature insect. Salamanders cor- 

 respond in development with the tadpoles or larvae of the tailless 

 Batrachians, and both possess to a large extent the power of re- 

 growth ; but not so the mature tailless Batrachians. 



Absorption often plays an important j)art in the repair of injuries. 

 When a bone is broken and does not unite, the ends are absorbed 

 and rounded, so that a false joint is formed ; or if the ends unite, 

 but overlap, the projecting parts are removed.^ A dislocated bone 

 will form for itself a new socket. Displaced tendons and varicose 

 veins excavate new channels in the bones against which they press. 

 But absorption comes into action, as Virchow remarks, during the 

 normal growth of bones ; parts which are solid during youth become 

 hollowed out for the medullary tissue as the bone increases in size. 

 In trying to understand the many well-adapted cases of re-growth 

 when aided by absorption, we should remember that almost all 

 parts of the organisation, even whilst retaining the same form, 

 undergo constant renewal ; so that a part which is not renewed would 

 be liable to absorption. 



Some cases, usually classed under the so-called nisus formativus, 

 at first appear to come under a distinct head ; for not only are old 

 stxuctures reproduced, but new structures are formed. Thus, after 

 inflammation "false membranes," furnished with blood-vessels, 

 lymphatics, and nerves, are developed ; or a foetus escapes from the 



^ Carpenter's ' Principles of Comp. Phys.,' p. 479. 

 Physiology,' 18o4, p. 47 9. ^ Prof. Marey's discussion on the 



■* Chariesworth's ' Mag. of Nat. power of co-adaptation in all parts of 



Hist.,' vol. i., 1837, p. 145. the organisation is excellent. 'La 



^ Paget, 'Lectures on Surgical Machine Animale,' 1873, chap. ix. Sef. 



P',thology,' vol. i. p. 239. also Paget, ' Lectures,' &c., p. 257. 



6 



Quoted by Carpenter, *Comp. 



