Following administration of deuterium to white rats changes of dysimmunitary-immunitary depression occurred. At the beginning the changes involved the whole spleen parenchyma, with marked lymphocyte depopulation of the red pulp and a decrease of the lymphod follicles. After about 4 - 7 days important amorphous deposits were formed, located exclusively perifollicularly and only in the spleen. The authors suggest the dysimmunitary globulinic-paraamyloidic nature of these deposits which, in their opinion, are produced by deuterium through a chemical mechanism. The differential diagnosis was only made with Gamma-Gandy nodules, because no such changes are found in pathology. It is not known why this deposition takes place exclusively in the spleen and especially around the lymphoid follicles. The authors raise the question whether some methods could be found which might direct the immunitary blockade to certain organs.