XII 



ON THE LIMITS OF DIVISIBILITY OF LIVING MATTEK 1 



1. THE progress which has been made in physics and 

 chemistry as the result of our modern conceptions of mole- 

 cules and atoms suggests the possibility that a more definite 

 insight into the limits of divisibility of living matter might 

 also be of importance for the development of physiology. 

 As a criterion for "living matter" we might use the irrita- 

 bility or spontaneity. But as the "spontaneity" of living 

 matter is in its simplest form (in Amoebse) apparently not 

 different from the physical phenomenon of spreading, for 

 this criterion the limits of divisibility of living matter coin- 

 cide with the limits of this purely physical phenomenon. 

 But spontaneity is neither the deepest nor the most essential 

 life-phenomenon ; development or, in other words, growth, 

 organization, and reproduction occupies this place. If we 

 ask how the ultimate elements of living matter are con- 

 stituted which still possess the specific rnorphogenetic prop- 

 erties, the excellent papers of Nussbaimi give us a qualitative 

 answer. This investigator found in experiments on the 

 divisibility of an Infusorian, Gastrostyla, that only such 

 pieces are able to regenerate into a complete animal as con- 

 tain nuclear material. 



For the preservation of an Infusoriau it is immaterial whether 

 it is divided longitudinally, transversely, or obliquely; if only a 

 portion of the nucleus is retained, the fragment regenerates into its 

 original form in less than twenty -four hours, depending upon the 

 temperature. As soon as twenty minutes after division the cut 

 edges form new cilia, and upon the following day each of the 

 pieces containing nuclear material possesses from four tosix nuclei 

 and nucleoli, and all the ciliary appendages characteristic of the 

 species. 3 



1 Pfliii/crs Ar<-hi,\ Vol. LIX (1894), p. 379. 



2 NUSSHAUM, An-ltii' fur ini/.-riinLn/iisr/n- A n<ituii<i<. Vol. XXVI, i>. .">! I. 



