THE GREAT-CRESTED GREBE. 
183 
the Podiceps cristatus this tubular prolongation was full of feathers, 
which consisted of the shafts and barbs deprived of the barbules. These 
were not wound up confusedly in a ball, but lay parallel to each other 
and to the long axis of the tube. In the general oavity there were a 
large quantity of feathers, many fish-bones, portions of coleopterous 
insects, and a few pieces of the firm stems of vegetables. Some of the 
feathers are perfect, but slightly broken ; others with the shaft and 
barb, but without the barbules ; or the barbs alone, the shaft and 
barbules being removed. Had I not carefully examined the gradual 
but progressive alteration in the general cavity, I would undoubtedly 
have said that the tubular prolongation was occupied by a bundle of 
hairs, and not feathers, so close is the resemblance. The amount of 
barbules in the gizzard far exceeds that of the barbs or shafts, so much 
so, that it would require twenty times the number of feathers to pro- 
duce an amount of barbules equal to those present. The bones in the 
gizzard seem to be little if at all acted upon by the proventricular 
fluid, and, from the thickness and density of the inner coat, it is pro- 
bable that there is no secretion except that fluid. Now these circum- 
stances deserve consideration, as they seem to imply that the proven- 
tricular fluid, which dissolves the soft parts, has no action whatever 
upon the bones, and that they, after being triturated, especially in the 
tubular prolongation of the gizzard, pass onwards into the small intes- 
tine, and there being mixed with the biliary and other secretions, form 
the dark-coloured and friable masses found in its upper part, which, as 
they pass onwards towards the vent, are gradually assimilated and con- 
verted into fluid excrement. 
“ In the gizzard of Podiceps rubricollis there are, comparatively, few 
feathers, and they are also less worn. There is also a less degree of 
muscularity, and a more perfect solution of the solid parts of its food 
by the proventricular fluid. From the preceding observations I infer 
that the feathers perform a threefold office. First, as a protecting 
medium, to defend the epidermic coat from laceration by the sharp 
edges and points of the fish-bones. Secondly, as a triturating appa- 
ratus. Thirdly, as a filter, the tubular prolongation allowing the fluids 
and triturated bones to pass into the intestine, whilst the coarser por- 
tions are retained, to be subjected to further action . 55 
