Experiments on the effects of the grit feeding upon the development of the gizzard sac and the gizzard were conducted with a total of 100 male day-old white Leghorn chicks. They were secured in two groups fed all mash ration with grit and without grit until 10 weeks of age. At every week of age each of the gizzards was observed by X-ray and some of the chicks which showed typical figures were killed.
1) In the observations by X-rays at every week of age a distinct difference was noticed in the shape of gizzard sac between two groups, the very glovular form in the group with grit (Plate 1, Figs 1, 3, 5, 7), but the slender in the other without grit (Plate 1, Figs. 2, 4, 6, 8).
2) In the gizzard contraction, time and resting pause were shorter and contracted more frequently per minute with grit.
3) Much quantity of grit had been similarly retained in the gizzard respectively, however, with the age proceeding, some marked differences in the quantity of the retained grit were noticed (Plate 1, Figs. 1, 3). But till 4 weeks of age any effects of the quantity of the retained grit upon the gizzard development were not perceived (Plate I, Figs. 6, 8, Plate 2, Figs. 9, 10).
4) The feeding grit caused a remarkable increase in the size of the transversal axis and the weight of the gizzard (Text-figs. 2, 3, 4 ).
5) The gizzard development in every period was thoroughly ascertained through the figures by X-ray observation.
6) It is concluded that the grit retained in the gizzard caused the dilation of the gizzard sac, and accelerated the vigorous movements and hence the development of the muscle layers of the gizzard may be improved.