In preliminary experiments with fresh dog thyroids, it was found that, if glands were allowed to autolyze in a sterile moist chamber, the colloid became gradually vacuolated and finally disappeared. The vesicles were then packed with desquamated epithelial cells, and the gland presented a solid cellular appearance. The process was accelerated if the tissues were kept in the incubator. From the experiments and subsequent examination of 70 thyroids of new-born infants, it was concluded that the disappearance of colloid and des-quamation of epithelial cells must be regarded as postmortem degeneration, and that the thyroid of the newborn is normally composed of small vesicles lined with cubical epithelium and filled with colloid. Variation in appearance of the thyroid was fouad to be related to length of time which elapsed between death or stillbirth and postmortem examination. No relation was found between the condition of the thyroid in the full-time fetus and the development of the child as reckoned by extent of ossification or any body measurement.