1. A histological method is described for a study of post-mortem cytoplasmic changes; the method depends upon observed variations in staining capacity.
2. By the application of this method, a series of cytoplasmic changes were found in ox pituitary glands which had been exposed, after the death of the animal, for varying times to different temperatures. These changes correspond to alterations in the biological activity and chemical content previously investigated.
3. These methods showed that freezing apparently causes no alteration in the distribution of biological activity.
4. It is possible that the histological appearance can be used to determine the suitability of ox pituitary glands for the preparation of active extracts of the anterior lobe.