EXPERIMENTS WITH OSTRICHES—XII. 
LOW WEAKNESS AND DENSITY OF FLUE ARE PRODUCED. 
By Professor J. E. DuzrpEen, M.Sc., Ph.D., A.R.C.S., Rhodes University 
College, Grahamstown. 
A clipping of spadonas recently received from Mr. F. R. Edwards, 
Wijers River, through the Editor of the Agricultural Journal, is of more 
than passing interest, in that it sheds much light upon the influence of 
nutrition and blood-pressure in the production of a weak or a dense flue. 
One of the feathers is shown in the accompanying photograph (Fig. 1), 
and differs from ordinary plumes in presenting an almost entire absence 
of barbules on the flue. The shaft and also the barbs coming from each 
side of it are normally developed, but only here and there can the merest 
traces of the barbules be recognised. Such a feather would be practically 
valueless for the usual purposes for which ostrich plumes are employed. 
While such extreme cases are rare, it is by no means unusual to find plumes 
in which the barbules are shorter than desirable, either over the entire 
feather or in places. 
THe SrRuctuRE AND NuTRITION OF A GROWING FEATHER. 
To understand how such a plume as that shown has been produced 
requires a knowledge of the microscopic characters of the feather at its. 
earliest stage of growth and also of its method of nutrition ; but such a know- 
ledge is well worth a little trouble to acquire from the explanation which it 
affords of many other problems connected with feather growth. If a thin 
cross section be made of a feather, while it is still soft and plastic in the 
lower part of the feather socket, the following parts will be recognised, and 
are diagrammatically shown in Fig. 2. The middle or interior of the 
feather is occupied by what is known as pith or medulla. This consists 
of a tissue of loose cells, among which is an extremely rich supply of blood- 
vessels—arteries, veins and capillaries. The blood is for the nourishment 
of the growing feather, and one easily realises how rich is the supply by 
the amount of bleeding or hemorrhage which takes place when an unripe 
feather is clipped or punctured in any way; also when it is remembered 
that a wing feather grows at the rate of about a quarter of an inch a day, 
the need for such a copious supply of the nutrient blood is apparent. As the 
feather ripens the blood drains from it and the pith dries up, the space it 
occupied then becoming filled with air. 
At the outer surface of the pith is a layer of cells which gives rise to 
the horny sheath of the medulla. This sheath is best seen in the older parts 
of the growing feather, and remains as a horny tube in the middle of the 
unopened feather after the pith dries up. As the feather expands it is, 
