108 THE GROUSE IN HEALTH AND IN DISEASE 



invariably found that the grains of grit are fewer and smaller 

 than in the larger and full-grown specimens. The gizzard of 

 a Grouse chick of fourteen to twenty days old was examined, 

 and the grit was found to weigh 3 grains. It consisted of frag- 

 ments of quartz, smooth and water- worn, and evidently picked 

 up in the bed of a stream. Two minute but perfect prisms of 

 quartz, were also found. All the grains were decidedly smaller 

 than in an adult. In a half-grown chick the grit weighed 

 58 grains, while in adults the average weight is 118 to 120 

 grains. Grits are present even in very young birds ; in one 

 case they were found in a chick only forty-eight hours old. 



The grit of an old bird can be at once recognised by the 

 large size of the grains, and by the excessive polish and smooth- 

 ness of the well-worn surfaces, suggesting that the larger grains 

 are in use for a considerable period of time. Between extreme 

 youth and old age all stages of wear and polish may be found, 

 as well as every gradation in point of size. 



A full analysis of the petrological character of the speci- 

 mens is contained in the Interim Report of the Committee ; 

 it is unnecessary to repeat all the details here, but a short 

 summary of the general conclusions may be given. As would 

 naturally be expected the constituents of these samples are 

 nearly always hard rocks and minerals. Minerals or rocks 

 softer than quartz, flint, or felspar are hardly ever found ; 

 this may be due partly to selection by the bird, but it must 

 also be borne in mind that soft substances would soon be ground 

 up by the action of the gizzard, and disappear. To this also 

 is probably due the almost complete absence of any calcareous 

 matter, which is both soft and comparatively soluble. The 

 only really abundant constituents in the gizzards of Grouse are 

 quartz and felspar, and small fragments of various rocks com- 

 posed of one or both of these minerals, such as granite, gneiss, 

 quartzite, etc., with occasionally grains of shot and crystals 

 of garnet, and other minerals. Felspar is chiefly found in 

 specimens from Scotland and North Wales, where rocks con- 

 sisting largely of this mineral are specially abundant. The 



