ACTINATION OF STARFISH EGGS BY BUTYRIC ACID. 153 



larval structures in metamorphosis), and the translocation of 

 reserve materials; the utilization of tissue-proteins in starvation 

 also appears to be dependent upon autolysis. 1 



The recent studies of Bradley and his associates have thrown 

 an interesting light upon the conditions under which acid pro- 

 motes autolysis of liver-cells. 2 Apparently the acid does not act 

 simply by rendering the reaction favorable to the activity of the 

 cell-proteases, for increasing the acidity does not necessarily 

 increase the hydrolysis of all proteins; 3 moreover certain foreign 

 proteins like gelatine or peptone are readily digested in neutral 

 or slightly alkaline solution in which the liver-proteins resist 

 digestion. It would appear that the intracellular proteases are 

 capable of activity under these conditions, provided they are 

 furnished with the appropriate substrate. The essential action 



1 Cf. Lane-Claypon and Schryver, Journal of Physiology, 1904, Vol. 31, p. 169; 

 Schryver, Biochemical Journal, loc. cit. In "Senescence and Rejuvenescence," 

 Chapter 2, Child calls attention to the general importance of the process of reduc- 

 tion or regression during development and regeneration. Regaided in the purely 

 chemical sense, regression is the reverse of construction; strictly speaking, both 

 processes are constantly and simultaneously at work in any living organism; it is 

 only when regression exceeds construction that the substance of the organism 

 undergoes visible decrease. Local regressive changes of this kind appear always 

 to accompany regeneration; the translocation of mater'al from one part to another 

 is a necessary condition of the process; and such evidence as we possess indicates 

 that autolysis is an important factor in any local structural breakdown which 

 furnishes the material required for construction elsewhere (cf. Sehryver's observa- 

 tions on the increased rate of autolysis in the livers of fasting animals, loc. cit.). 

 It must be admitted, however, that this evidence is deficient in many respects 

 (cf. Morse, Amer. Journ. of PhysioL, 1914, Vol. 36, p. 145), and it seems likely 

 that the essential factors in the disintegration as well as in the building up of 

 structure are unknown at present. The possible role of autolysis in regeneration 

 has been discussed recently by Loeb ("The Organism as a Whole from the Physico- 

 chemical Viewpoint," Putnams, 1916, p. I7S1; if autolysis is a factor in regenera- 

 tion, we may safely assume that it is important in developmental processes in 

 general, including the development of the organism from the egg, and in this case 

 probably from the very first, as suggested in the hypothesis put forward in the text. 



2 Bradley and Morse, Journal of Biological Chemistry, 1915, Vol. 21, p. 209; 

 Bradley, ibid., 1915, Vol. 22, p. 113; Bradley and Taylor, ibid., 1916, Vol. 25, pp. 

 261, 363. 



3 The liver proteins are very sensitive to increase of acidity (Bradley and Taylor, 

 loc. cit., 1916, p. 262), but foreign proteins added to the autolyzing mixture may or 

 may not show increased digestion under these conditions; e.g., the digestion of egg 

 albumin is greatly increased by acid, while that of casein and peptone remains un- 

 altered ; MnCh promotes the digestion of liver-proteins, but not that of egg-albumin. 



