249 



" about on the log. A few moments elapse, when the bird 

 " draws the whole of its feathers close to its body, and, stretch- 

 " ing itself ont, beats its sides with its wings in the manner of 

 " a domestic cock, but more loudly and with such rapidity of 

 " motion after a few of the first strokes, as to cause a tremor of 

 '• the air not unlike the rumbling of distant thunder .... 

 " . it may be heard a distance of two hundred yards. . . ." 



By means of a tame bird, and four cameras focussed on to 

 the particular spot on the log which had been selected by the 

 Grouse for his performance, Dr. Hodge secured forty negatives 

 in two days, and is able to tell vis authoritatively where the 

 error precisely lies in the above graphic account. " Some of the 

 " back feathers are drawn close, but tlie tail is spread some- 

 " what, the ruff is pai'tially erect and the feathers of the neck, 

 " breast, and particularly the sides, are much puffed out." 

 The airsacs of the ])reast and abdomen being distended with 

 air, and the side feathers being drawn strongly back to the 

 skin it is then seen that " a wide strip of bare skin is exposed 

 " down the mid-line of the abdomen." Hence the " contour 

 " surfaces of the strong wing supports along thesides are made 

 " to enclose a large cavit}' filled with air, and this acts like the 

 " resonance chamber of a drum and yields the booming throb 

 " to the air " on the impact of the rapid blows of the wing. 

 Did the wings beat on the solitl body of the bird " the stroke 

 " of the wing would produce a sharp slap instead of a resonant 

 " tone." One of the photographs, taken before a white sheet, 

 well illustrates the e.xtreme rapidity of the wing strokes during 

 one stage ol the drummiug, for they appear as little else than a 

 mere shadow or cloud, while the rest of the bird is in sharp 

 relief. 



From Dr. Hodge's observations it would appear that the 

 drumming is purely a mate call, and is moreover a fundamental 

 action on the part of the species, not due in the birds of any 

 one generation to mimicry of those of the preceding one. 



AVIAN TUBERCULOSIS :— This subject is attracting con- 

 siderable attention. Not only is there the able letter from Dr. 

 Snell which will be found on another page, but I have also 

 received several private and sympathetic communications on 

 the subject. One of these, from a member belonging to 

 the medical profession and a perfectly friendly critic, rather 

 indicates however his not having properly grasped the point 

 for which I have all along contended. He emphasizes the 

 fact that Avian Tuberculosis is " still adhered to " in 



