12 
growing feather which is indented to form the bar. A broad bar can 
never be produced even by continued shrinkage ; all that happens in this 
case is that the sheath wrinkles more and more deeply upon the soft 
feather and interferes to a greater degree with the formation of the 
barbules and barbs, and even indents the shaft. The night rings are about 
a sixteenth of an inch in height, and this is usually the vertical extent of 
a bar. 
PRODUCTION OF THE Bars SouvED—THE PROBLEM AS TO THEIR PREVENTION. 
While in the above account we may claim to have solved the problem 
as to how the bars in ostrich feathers are produced, there yet remains the 
greater question as to how their formation is to be prevented, which is 
really the practical issue with which the farmer is concerned. From what 
is established we can understand that the object at which to aim im pre- 
venting the bars 7s to maintain the blood-pressure within the growing 
feather at as uniform a rate as possible during both day and night; 
uniformity of conditions during the feather growing period is the 
key to success in the elimination of the bars. By maintain- 
ing this uniformity we may hope to minimise the difference in the 
feather growth during the day and night periods, and also give no oppor- 
tunity for a mechanical collapse consequent upon a_ considerable 
reduction of pressure. Anyone acquainted with the physiology of animals 
will, however, realise the difficulty of maintaining practical uniformity 
cf blood-pressure in organs which project so much beyond the general 
surface of the body as do the growing feathers of the ostrich, and which 
at the same time have such a rich supply of blood within them. The great 
difficulty is to overcome the variations in individual feathers, for usually 
it is not an interference with the growing feathers as a whole, but merely 
an example of the slight variation in blood-pressure to which any organ or 
part of an organ may be subject. 
The relationship between blood-pressure and feather perfection in the 
ostrich appears to be of such a delicate nature that any slight disturbance 
is productive of faults. Indeed under ordinary farming conditions this 
delicacy of relationship is never quite maintained, and we rarely get a 
plume showing perfection of growth. We can, however, enquire as to the 
conditions under which it is least likely to be disturbed. 
In the course of the experiments a great deal of evidence has been 
accumulated as to the conditions under which the blood-pressure varies, 
in other words as to the conditions under which bars are and are not 
produced. As would be expected, the conditions are very varied, but it 
can be accepted that they are largely, though not wholly, concerned with 
the nutritive condition of the bird. Something also seems to depend upon 
the exposure of the individual feather. For it has been seen that odd 
feathers growing out of time, and therefore not covered and protected 
by the others in a full crop, are very liable to be barred; also a slight 
variation in blood-pressure would have a greater proportional effect upon 
single feathers then upon the members of a full crop. 
There is plenty of evidence which proves that with strong vigorous 
birds kept in a good condition of health, little trouble need be feared 
from the presence of bars, where a full crop is being produced. The 
maintenance of the proper nutritive state of the ostrich, however, involves 
a thorough practical experience of the bird under its various phases. and 
often individual birds are somewhat out of feather-growing condition 
when not suspected. What is called for is a strong supply of blood to 
maintain a constant and regular stream to all the growing feathers under 
the many variations to which the domesticated bird is subject ; anything 
