106 INTERRUPTION OF NORMAL CHANGES. 



very seriously impaired. It indeed soon grows old, 

 wMle all the rest of the body may remain young. 

 Its imperfect action deranges other processes of the 

 body, and these react upon it until further action 

 becomes impossible, and death results. The gradual 

 but continuous and regular decay and renovation of 

 an organ is normal in the vertebrate animal. The 

 changes exhibit wonderful elasticity within certain 

 limits, according to the demand for functional activity 

 of the organ, but these limits, narrow in some, wide 

 in others, cannot be exceeded without derangement 

 and slow deterioration resulting. 



154. Interruption of normal changes. — This con- 

 tinuous renovation of an organ and accumulation of 

 the skeleton of its earlier periods of existence may, 

 however, be almost^ suddenly interrupted. In those 

 changes which lead to the foi'mation of pus the re- 

 moval of every texture is as perfect as during the 

 pupa state of an insect, biit the bioplasm constituting 

 the pus corpuscles has no power to give rise to that 

 which will take part in the development of new 

 tissues, while that which takes part in the removal of 

 the larval tissues during the pupa state does possess 

 this power. When therefore in vertebrata this complete 

 change occurs the organ is destroyed, but a new one 

 is never developed in its stead. A part of a complex 

 organ may be destroyed and removed, but it cannot 

 be formed anew, so tliat in man the gradual or sudden 

 destruction of a great part of an organ necessary to 

 life cannot be repaired, although in many cases the 

 patient may adapt himself to the altered state of 

 things and live under the changed conditions. Tlie 

 • above considerations aflFord, I think, an explanation 

 of the formation of the so-called interstitial indefinite 

 connective found in gi'eater or less amount in all 

 organs of all vertebrate animals, and of its increase 

 as age advances. The more regulai-ly, gradually, and 

 perfectly the changes are effected, the smaller will be 



