Summary.In 9 animals, previously treated with emulsion of cod liver oil up to the highest degree consistent with life, a study is made of the behavionr of the Ecg. for the following 7 1/2 months, as well as of the morphology of the hearts of these animals when they were killed.The Eeg. appears gradually to regain the normal, as the a—v‐conduction time and the QRS‐time are reduced from their prolongation, reached during the oil treatment, and the outlines of the curves as well gradually look more normal. A complete restitution, however, is not reached, and in most of the animals the archaism of contraction of the heart seems to be permanently somewhat altered, in as much as the last curve evidently differs from the initial one.The anatomical lesions of the heart of the animals, with one striking exception, are less prominent than in control animals, which died or were killed when under influence of the same amounts of oil. No example of complete anatomical healing of these lesions is proved in any animalThe best and most clear anatomical healing was reached when, after cessation of the dosing with c.l.o. the animal received a better diet than the basal diet used during the medication.On average therefore, a tendency of consolidation is found, which as to the function would possibly have been even more advanced if the animals had survived for a longer time.In the light of the experience from these experiments one can understand, why cod liver oil injuries are not known in human hearts from individuals once treated with even large quantities of oil.However, as it is exceptionally found that almost all the injuries arisen, from any cause may persist or perhaps even advance after the oil has been omitted during the comparatively long time, for this species of animal, of 7 1/2 months, it seems not impossible, that a cod liver oil treatment in man may cause a chronic heart disease.As far as these experiments show it, smaller heart‐lesions may possibly persist after a medication with cod liver oil for a fairly longer period