THE INFLUENCE OF REGENERATING TISSUE ON THE ANIMAL BODY. 



By Charles R. Stockard. 



When the adult animal body begins to regenerate new tissue in 

 order to replace a lost part, or when abnormal secondary growths arise, 

 the condition of growth-equilibrium is disturbed and such a disturbance 

 is followed by changes which affect the usual physiological condition of 

 the body. The question arises whether the changes following or accom- 

 panying normal regenerative growth are in any way similar to those 

 effects resulting from malignant or abnormal secondary growths. If one 

 believe, with many pathologists, that cancerous formations are growths 

 of a secondary nature induced by some derangement in the normal growth 

 states, and are not of infectious origin, then normal secondary growths, 

 in some stages at least, should affect the body in a manner somewhat 

 similar to that resulting from an active tumor growth. The emaciated 

 or cachectic conditions of the body resulting from the effects of cancerous 

 growths are not always thought to be attributable to toxins or sub- 

 stances taken into the circulation from the cancer, but at times seem 

 to be due to the excessive appropriation of nutriment and energy by the 

 rapidly growing cancer itself. A malignant tumor continues to grow 

 and so finally kills the body, while on the other hand the regenerating 

 part, although rapidly growing at first, gradually decreases in growth 

 rate and begins to differentiate and function, thus diverting the energy 

 previously used in the growth processes. 



I showed in the second of my "Studies of Tissue Growth" (Jour. 

 Exp. Zool., vol. VI, 1909) that the medusa disk of Cassiopea xamachana 

 decreased rapidly in size while regenerating new oral-arms, and that the 

 rate of decrease was faster in those specimens regenerating the greater 

 number of parts. In these experiments a source of error was realized, 

 since those specimens with 6 or 8 oral-arms removed might have been 

 deprived of more reserve food held in the oral-arms than had the individ- 

 uals which lost fewer arms. I determined to control this condition by 

 operating on medusae so as to remove the same number of oral-arms from 

 all and to increase the amount of new regenerating tissue in some individ- 

 uals by also removing a part of the disk. The specimens were kept under 

 identical conditions and were not fed during the time of the experiment. 

 Thus any difference in their responses is due only to the additional 

 amount of regeneration imposed upon the individuals with the cut disks. 



Emmel (36th Ann. Rep., Inland Fisheries of Rhode Island, 1906) 

 has contributed an observation which is most interesting in connection 

 with these experiments. He found that when larval lobsters were regen- 

 erating new legs they molted after longer intervals than normal individ- 

 uals, and grew in size at a rate sometimes 24 per cent slower than the 

 non-regenerating specimens. Most important was his observation that 



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