V CONCLUSIONS CONVERGENCE OF CONCEPTS 535 



tion of animal cells than enzymatic adaptation are represented by investigations 

 of spore germination as well as similar investigations on spore formation. Spore 

 formation (for review see Foster, 1956) for example, is initiated when vegetative 

 proliferation ceases. Antigenically new material is formed in the course of sporula- 

 tion and once sporulation is induced the bacterial cells cease to react to an inducing 

 substance with formation of adaptive enzymes, indicating a restriction of the 

 potentialities of the PFS similar to that observed in embryonic determination. Also, 

 overall acceleration of protein synthesis by the addition of glucose to the medium 

 leads to a suppression of sporulation. This may be regarded as an example of 

 metabolic regulation of protein formation. 



Hachisuka et al. (1956) recently have shown that the enzymes of the glucose 

 oxidizing system of Bacillus subtilis do appear in a step-wise fashion with the 

 development of distinct morphological phases in the transformation from a spore 

 to the vegetative cell. The possibility that the failure to detect, in bacterial spores, 

 enzymes which occur in the vegetative forms of the same bacterium is actually due 

 to the insensitivity of the analytical methods used has been considered (Church, 

 Halvorson and Halvorson, 1954). 



For a considerable time before adaptive enzyme formation in bacteria became 

 known, one type of induction of protein formation in metazoan tissues had been 

 demonstrated; viz. antibody production in response to a foreign protein. The 

 relevance of antibody production as a model for the activity of the PFS of develop- 

 ing cells has been fully appreciated by Tyler (1947, 1955) and Weiss (1947, i955). 

 The essential points in interpreting antibody formation in this sense can be stated 

 as follows. Injection of an antigen elicits in certain cells of the mature organism 

 formation of a new protein, the antibody. This protein is structurally related to 

 the antigen, giving rise to a highly specific interaction between the two proteins 

 in the formation of an antigen-antibody complex. Antibody formation may con- 

 tinue for many years after the transient exposure to the antigen. This must mean 

 that the initial response to the antigen becomes more or less permanently fixed in 

 the PFS of the responding cell. In explaining this persistence, two hypotheses have 

 been suggested. Either the antigen itself becomes a part of the antibody-forming 

 system of the cell or it changes, in a specific way, the structure of this system so that 

 production of proteins, structurally related to the antigen, becomes irreversibly 

 established. These steps in antibody formation are analogous to the production of 

 new proteins in the process of induced enzyme formation and possibly in diflferen- 

 tiation where the inducing conditions provide the trigger and in part the control 

 for the PFS of the responding cell. That a further elucidation of this alternative 

 was achieved by an analysis of the properties of embryonic tissues is an important 

 additional demonstration of the interaction of research in embryology and immu- 

 nology. The remarkable phenomenon first recognized in its significance by Burnet 

 and Fenner (1949) consists in the failure of embryos to form antibodies against 

 certain heterologous proteins and to remain unresponsive to immunological 

 stimulation during post-natal life'. This absence of immune response can be 



1 Experiments in which this phenomenon could not be confirmed were published by Bauer 

 et al. (1956). 



Lileralure p. sjg 



