In the second chapter we mentioned the interesting idea of Armstrong that when a synthesis is brought about by a digestive enzyme (_e. g._, maltase) not the original substrate is formed (_e. g._, maltose) but an isomer, in this case isomaltose; and this isomer is not attacked by the enzyme maltase. We thus get a rational understanding of the statement which Claude Bernard used to make but which remained at his time mysterious: _la vie, c’est la création_. During life, when nutritive material is abundant, through the reversible action of certain enzymes, synthetic compounds are formed from the building stones furnished by the blood. These synthetic isomers cannot be hydrolyzed by the enzymes by which they are formed and hence on account of the isomeric structure are immune against destruction. It is not impossible that the increase of the concentration of acid in the cells after death transforms the isomers into that form in which they can be digested by the enzymes contained in the cell. Another possibility is that the increase in digestibility brought about by an increase in C_{H} in the cell is due to the hydrating effect of acids on proteins with a subsequent increase in digestibility. Whatever the answer may be, the work done since Claude Bernard has removed that cloud of obscurity which in his days surrounded the prevalence of synthetic action in the living and of disintegration in the dead tissues. 3. We have already referred to the connection between the lack of oxygen and the onset of autolysis and disintegration of tissues in the body. It is of interest that there are cells in which the disintegration under the influence of lack of oxygen is so rapid that it can be followed under the microscope. The writer has observed that certain cells undergo complete irreversible dissolution in a very short time under the influence of lack of oxygen, _e. g._, the first segmentation cells of the egg of a teleost fish _Ctenolabrus_.[300] [300] Loeb, J., _Arch. f. d. ges. Physiol._, 1895, lxii., 249. [Illustration: FIG. 48] [Illustration: FIG. 49] [Illustration: FIG. 50] [Illustration: FIG. 51]