166 THE GROUSE IN HEALTH AND IN DISEASE 



almost exactly as it is plucked from the living plant, and 

 it is found thus in masses fresh and green, or greenish brown, 

 with no appreciable admixture either of mucus or of water. 

 Probably when there is food in the crop, no water is drunk, 

 for there is never any wetness either in the crop, proventriculus 

 or gizzard, all of which are occupied in turn by the morsels of 

 food in process of digestion. 



From the proventriculus the bits of food, coated now with 

 a tenacious and slightly acid mucus, are passed into the 

 muscular gizzard (PL xvi.), a familiar object in the anatomy 

 of the common fowl, and an organ of very similar shape and 

 of equal muscularity in the Grouse. Its walls are very thick, 

 and the muscles which compose them act from tendinous 

 sheets, into which they are firmly fixed. The cavity 

 of the gizzard is comparatively small and contains about a 

 teaspoonful of small hard subangular or rounded grains of hard 

 rock. The substance almost universally chosen as grit by the 

 Red Grouse is quartz, and although on the moor, as in captivity, 

 the bird will swallow any small portion of hard material which 

 comes in its way, quartz is most suitable, not only for the Grouse 

 but for every other graminivorous bird in health. The subject 

 is more fully dealt with in chapter iii. 



The food having reached the gizzard with a free admix- 

 ture of slightly acid mucus, is now thoroughly mixed up 

 with the grits of quartz, and ground with their assistance to 

 a pulp, the harder woody fibres soon showing up as whitish 

 bits in a brownish, greenish, or reddish mess. This vegetable 

 pottage has now to be separated from the quartz grits, and 

 to be passed little by little into the duodenum. 



The separation is effected by the sphincter or ring-like 

 muscle at the exit from the gizzard, and the digestible food, 

 including our particle of heather, now sufficiently pulped, is 

 separated as it leaves the gizzard from most of the harder and 

 larger grits, and enters the duodenal loop of the small intestine. 



The duodenum (PL xvi.), 6| inches in length, begins 

 at the exit of the gizzard and is U-shaped. It consists of two 



