4 
by the bird as the feather ripens, and thus allows the flue inside to open 
out. 
It is necessary to bear in mind that in the growing feather the blood 
and blood-vessels are confined to the pith; as already stated, no blood- 
vessels are ever found among the cells which form the actual feather. The 
cells forming the feather substance correspond with those which constitute 
the outer layer of our own skin (epidermis), and also give rise to the cover- 
ing cf hair; this outer skin in ourselves also is devoid of blood-vessels and 
nerves. The pith or medulla of the feather ccrresponcs with our under- 
skin (dermis), which is well supplied with both nerves and blood-vessels. 
This being the case, it is manifest that the cells forming the feather must 
receive their nourishment by exudation of the fluid part of the blood 
through the thin walls of the vessels in the pith, and the blood-plasma must 
pass by diffusion among all the cells as far as the surface or feather-sheath. 
The cells nearest the vith will receive their nourishment first, and these 
are the cells which will ultimately give rise to the barbs, while those more 
distant, which give rise to the barbules and feather-sheath, will get their 
supply of nutritive fluid later. Should there be a deficiency in the nutri- 
tion of the growing feather the barbule-forming cells will suffer first, and 
the barb-forming cells later. 
Propuction oF FEATHERS WITHOUT BARBULES. 
With the above facts before us as to the nature of the growing feather 
and its nutrition, we are in a position to understand the production of a 
feather devoid of barbules, such as that shown in Fig. 1. For some reason 
the amount of nutritive fluid exuding from the pith to the feather-forming 
cells around it has been sufficient to supply only the nearest cells, or those 
which give rise to the shafts and barbs; the fluid was absorbed before it 
reached the outer cclls which give rise to the barbules, and therefore the 
barbules are absent cr very imperfectly formed. The feather cells can 
only grow and multiply in proportion as they are supplied with nutritive 
materials from the blood, and either from lack of quantity or insufficient 
prossure, these materials have not penetrated to the barbule-forming cells. 
Without an examination of the chick at the time the feathers were 
growing, or a knowledge of its food and surroundings, it is impossible to 
say what was the cause of such a defective nutrition of the feather; but 
whatever the cause, it must have been present all through the six months 
necessary for the growth of the spadona. The chick may have been in a 
very weak state of health from deficient food or some ailment, and hence 
the supply of blood to the growing feather was sufficient only for the cells 
forming the shaft and barbs; or, more probable, in its food was included 
some weed or grass, the action of which is to reduce the superficial blood- 
pressure, and therefore the pressure on the nutritive fluid was insufficient 
to force it to the cells furthest away from the central pith. This latter 
suggestion seems more likely from some recent experiences in Oudtshoorn 
described below. 
Since receiving the feathers, however, inquiries have been made among 
other ostrich farmers as regards the frequency of occurrence of birds with 
barbuless feathers, and some important facts have been elicited which call 
for a different interpretation. Mr. C. Gardner, of Harvest Vale, has sent 
a clipping of similar spadonas, and states that every feather on the bird, 
including the body-feathers, is of the same type. The bird is one of a large 
clutch of chicks, and none of the others are affected, although all the chicks 
have been treated alike. Mr. Lappan, near Grahamstown, also mentions 
an interesting case in which a bird from the chick stage onwards always 
gave a crop of feathers without barbules. None of the other birds in the 
