PHYSIOLOGY AND ANATOMY OF RED GROUSE lOl 



clie roots ; should this precaution be neglected the bird, having no notion what- 

 ever of using its feet to steady anything, drags the loose heather all over the 

 ground in unsuccessful efforts to pluck off the tips. 



There is sometimes to be seen quite a free flow of watery saliva from the 

 beak of a feeding bird, and in the mouth of birds killed there is always a certain 

 amount of saliva. This saliva serves to coat the rough hairy heather 



, , Saliva. 



tip with mucus, and thus to facilitate its passage down the oesophagus 

 to the crop (Pis. xxvii.a, XLiv.). The food is, of course, swallowed whole but in 

 very small pieces, and there is no mastication. The length of the oesophagus 

 (Pis. XXVI. oe., XXVII., Fig. 1 (a), xliv.) from the pharynx to the proventriculus 

 is 5| inches ( = 140 mm.), when the neck is normally outstretched; q, , 

 but before passing down the whole length of this tube the food finds S"^- 

 its way into a thin-walled sac or diverticulum of the oesophagus, at a point 

 3 inches, or 75 mm., from its entrance at the pharynx, and commonly called 

 the "crop" (Pis. xxvii.a, xliv.). Here the food collects, and 



Crop. 



remains for a longer or a shorter period according to the rate at 

 which the gizzard can dispose of it. The latter portion of the oesophagus 

 measures 2 inches ( = 50 mm.), in length, and the opening of the crop occupies 

 about 17 mm. of the front wall of the oesophagus. The proventriculus p,.oveji. 

 (Pis. xxvi. Pr., xxvii., Fig. 1 (b), xliv.) forming the thick- walled t"'^"!"^- 

 glandular part of the stomach has a cavity of very small dimensions, and a 

 length of f inch ( = 20 mm.). It is lined with large mucous glands having 

 prominent mouths. These secrete a thick, tenacious, opaque white fluid, where- 

 with the morsels of food on their passage from the crop to the gizzard are 

 coated. 



In this respect there is a very great difference between the condition of 

 the food as it leaves the crop, and its condition in the actual gizzard. In 

 the crop the food is almost invariably dry, 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. 



This almost universal dryness of the heather, or other Grouse food, as it 

 is found in the crop, militates strongly against the idea which is Foodiu 

 occasionally suggested that the Grouse is a thirsty bird by nature, nOT^^aHy 

 and must have an abundant supply of water. This is almost certainly ''''^'• 

 not the case, for the very rare instances in which the contents of the crop 



