In the Proceedings of the Physiological Society of 17th December 1904 (pp. 557, 564), the author gave a communication on the influence of a meat diet on the thyroid gland of rats which had been fed on meat for periods varying from six weeks to four months. The present investigation was undertaken to ascertain the effects of the same diet on the thyroid glands in the second generation of meat-fed rats. The thyroid glands of over fifty animals have been examined, with an equal number of controls. The ages of the rats varied from one day to three months; thirty of the series were under three weeks old, being unweaned at the time of death.

1 Chalmeis Watson, Journal of Physiology, vol. xxxiv.

The histological appearances of the thyroid glands of the meat-fed rats differed from those of the control glands. These differences were, as a rule, of a striking character; in a small minority (eight rats) they wire much less pronounced. The main appearances observed were the following: -

1. Great congestion of the gland, with entire absence of colloid, and little or no attempt at vesicle formation, the gland being in an unusually embryonic state. This appearance was only observed in the case of animals which died in a fortnight after birth. Eight animals.

II. An increase in the amount of the colloid, with thinning of the walls of the vesicles from pressure. This appearance was most pronounced in the case of animals whose weight and general nutrition at death was above the average of meat-fed subjects. Ten animals.

III. A diminution or entire absence of colloid with degeneration and shedding of the secreting cells. This condition was specially marked in the case of animals whose general nutrition was obviously defective. Fourteen animals.

IV. Types of glands illustrating a transition between II. and III. were found in ten animals.

The results of this investigation confirm the author's earlier observations in showing that an excessive meat diet induces structural changes in the thyroid gland. They further show that these changes may be present to a striking degree in very young animals (unweaned) which had not directly partaken of a meat regime.