212 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



A FEW REMARKS ON THE LIMITS OF REGUL ABILITY 



There has never been found any sort of " experience " in 

 regulations about morphogenesis or in adaptations of the 

 proper physiological type. Nothing goes on " better " the 

 second time than it did the first time ; l everything is either 

 complete, whenever it occurs, or it does not occur at all. 



That is the first of our important negative statements 

 about regulations ; the second relates to the phrase just 

 used, " or it does not occur at all." There are indeed limits 

 of regulability ; adaptations are not possible to every sort 

 of change of the physiological state : sickness and death 

 could not exist if they were ; nor is restitution possible in 

 all cases where it might be useful. It is a well-known fact, 

 that man is only able to heal wounds but is altogether 

 destitute of the faculty of regeneration proper. But even 

 lower animals may be without this faculty, as are the 

 ctenophores and the nematodes for instance, and there is no 

 sort of correspondence between the faculty of restitution 

 and the place in the animal kingdom. It is not altogether 

 impossible that there may be found, some day, certain con- 

 ditions under which every organism is capable of restoring 



1 The few cases of an "improvement" of morphogenetic acts in hydroids 

 described by myself are too isolated at present to be more than mere 

 problems (Arch. Entw. Mech. 5, 1897). The same is true, it seems to me, 

 with regard to certain recent discoveries made by R. Pearl on Ceratophyllum 

 (Carnegie Inst. Wash. Publ. No. 58, 1907) ; and by Zeleny on a medusa 

 (Journ. exp. Zool. 5, 1907). Pawlow's discovery, that the enzymotic com- 

 position of the pancreatic fluid in dogs becomes more and more adapted to 

 a specific composition of the food (either meat or bread and milk) the longer 

 such a specific composition is offered to the individual animal, may probably 

 be understood as a case of mere functional adaptation of the cells of the 

 digestive glands, if it stands criticism at all (see Bayliss and Starling, Ergeb. 

 Physiol. 5, 1906, p. 682). 



