GREY PTARMIGAN. 205 



entering the region of heath ; but in winter, during snow- 

 storms, they shift their residence, and betake themselves for a 

 while to a somewhat lower station. Their food consists of vari- 

 ous plants, chiefly of a shrubby nature. Thus, in the crops of 

 the individuals first described above, was contained a large 

 quantity of fresh green twigs of Calluna vulgaris, Vaccinium 

 Myrtillus, and Empetrum nigrum, the largest fragnients not 

 exceeding five-twelfths of an inch in length. Leaves and twigs 

 of Vaccinium Vitis-idaea, Salix herbacea, seeds of various 

 Juncese and Cyperaceae, and other plants, with berries in 

 autumn, also form part of their food ; which is thus, in fact, 

 for the most part the same as that of the Brown Ptarmigan. 



It is a remarkable fact that all the Grouse and Ptarmigans 

 which I have examined invariably select small fragments of 

 white or hyaline quartz to aid the trituration of their food in 

 the gizzard. Indeed, most of the phytiphagous birds do the 

 same, although I have also found in the gizzards of many of 

 them fragments of felspar, and in those of some even bits of 

 coal and other substances. The process of digestion and assimi- 

 lation is performed in the Grey Ptarmigan in the same man- 

 ner as in the Brown species and the Black Grouse ; but as 

 persons who enter into anatomical details have been accused of 

 neglecting physiological explanations, I may be permitted to 

 state the progressive changes which the food undergoes. 



The fauces and oesophagus, v/hich are smooth and even, are 

 profusely covered with a mucous fluid, which is more abundant 

 at the aperture of the crop. This organ is extremely thin and 

 but slightly bedewed. The proventricular glands exude a very 

 copious viscid juice. The inner surface of the intestine is vil- 

 lous, even, and constantly moist ; towards the entrance of the 

 coeca, its mucous coat is covered with flattened tapering pro- 

 jections directed upwards. The rectum is smooth and even 

 within, but in its upper part glandular and plentifully supplied 

 with mucus. The coeca are internally villous ; and excepting 

 at the commencement, have their inner coat raised into about 

 seven longitudinal white prominent lines, which are thick, vil- 

 lous, and appear externally through the muscular and perito- 

 neal coats. The walls of the intestine seem thick at the upper 



