1866.] Dr. John Davy on the Bones of Birds. 299 



(and they are of a very delicate nature), there is no perceptible effect of 

 motion upon radiation. 



In conclusion the authors desire to say that they are much indebted to 

 Mr. Beckley, who not only invented the apparatus, but assisted at all the 

 experiments, and without whom they could not have been performed in a 

 manner so satisfactory. They are also indebted to Mr. Atkinson for his 

 kindness in lending them a large gasometer, and to Mr. Browning and 

 Mr. Ladd for exceedingly true aluminium and ebonite disks. 



III. On the Bones of Birds at different Periods of their Growth.-'^ 

 By John Davy, M.D., F.R.S., &c. Received October 23, 

 1866. 



In this paper I beg to submit to the Royal Society the results of some 

 further observations on the bones of birds, and more especially on those 

 bones which in the adult contain air. 



In offering them, I would wish them to be considered as a continuation 

 of those communicated on a former occasion, and published in the Pro- 

 ceedings of the Society*. 



In engaging in the inquiry I have had two objects chiefly in view : one 

 to endeavour to determine whether at an early stage the bones, which at 

 maturity contain air, differ essentially from those of birds which are then, 

 and are permanently filled with marrow ; another, to endeavour to ascer- 

 tain in the instance of the former, the rate at which their early contents 

 are absorbed, or an approximation to the time that air takes the place of 

 the medulla. 



The birds of the first kind subjected to observation have been the follow- 

 ing : the common fowl, duck, goose, turkey, pheasant, partridge, grouse, 

 rook, common crow, owl, sparrow-hawk, buzzard, blue tit ; of the second 

 kind, the woodcock, blackbird, water-ouzel, marten, swift, greenfinch, tit- 

 lark, sparrow, stonechat, blackcap, yellow ammer, little sandpipe, canary. 



I. Of the Common Fowl. — Of this bird I have examined the bones at 

 different ages in a large number of instances. A few are selected as most 

 characteristic : — 



1 . Of a foetal chick taken from the egg on the fourteenth day of incu- 

 bation, the bones of the extremities were much advanced, the inferior more 

 than the superior. Their epiphyses were almost gelatinous ; but the shafts 

 were partially ossified, and had already some firmness. In both the 

 humeri and femora, medullary matter was found. It was of a red colour, 

 and under the microscope exhibited the usual character of this tissue. 

 Broken up, in each were seen numerous oil-globules, with which were 

 mixed blood-corpuscles and other corpuscles of a smaller size, some circular, 

 some of an irregular form. 



^ Vol. xiv. 337, 475. 



