1. All the features peculiar to the gross cysts of the thyroid gland which possess fluid contents appear to indicate that they are essentially of hæmorrhagic origin.
2. While these gross cysts would seem more especially to occur in glands which already present the features of parenchymatous goitre, the theory of Wölfler that they originate as a consequence of spontaneous rupture of the vesicles is unsatisfactory.
3. It would seem more probable that these large cysts are due to rupture, traumatic or otherwise, of some of the vessels of the organ. The frequent signs of small hæmorrhages in cases of parenchymatous goitre without evidence of associated gross change in the surrounding vesicles, the structure of the organ and its exposed position, all appear to favour this view.