1. Investigation of the changes occurring in Zymbal's glands showed that generalized hyperplasia was absent. The earliest changes involved the whole of a small sebaceous lobule in marked hyperplasia, with changes in both nuclear and cytoplasmic characters, and this progressed with both squamous and sebaceous characters forming an expansively growing tumor. Foci of squamous hyperplasia occurred less frequently. Tumors were not related to cystic changes in the ducts or to otitis media.

  2. The theoretical significance of the absence of hyperplasia in these glands, as compared with that seen in the liver of the same animals, in discussed.

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