I/O OSCAR RIDDLE. 



THE MEANING AND CAUSE OF THE DEFECTIVE LINES AND 

 OF THE SPACES BETWEEN THEM. 



We may now consider the significance of this blocking out of 

 the feather from end to end into bands, "bars," or plane feather- 

 elements, separated from each other by extremely faint depres- 

 sions or constrictions --for, my studies demonstrate that this is a 

 true conception of feather structure. 



That the feather from tip to tip does not represent a perfect, 

 uniform continuity, but is made up of an apposed series of faint 

 "fundamental bars" is a conception which I owe to Professor 

 Whitman. I have proved absolutely that the defective lines, or 

 points of apposition of the "fundamental bars " are the points at 

 which all of the defects appear, and are therefore, really minia- 

 ture representatives of the defective areas and constrictions of 

 types one and four. I think I have also proved that each block, 

 segment or " fundamental bar " of the feather represents a day of 

 growth, and this is at the same time the amount of feather-growth 

 between two low blood-pressures. Further, I have abundant 

 evidence that the defective lines and areas represent points devel- 

 oped under a diminished rate of cell-growth and cell-division, 

 brought about by a reduced nutrition, which is in turn the result 

 of a daily lowering of the blood-pressure. This low blood-pres- 

 sure doubtless occurs between one o'clock A. M. and six A. M. 



The evidence that a single "fundamental bar" and a single 

 defective line or area are laid down each day, and that this is the 

 total of a day's growth is conclusive. In very favorable material 

 I have been able to show, for example, that a feather 56 days 

 old shows 56 "fundamental bars" and 56 defective lines, areas 

 and constrictions. That the defective area is laid down at night 

 and during a period of low blood-pressure, I have demonstrated 

 twice experimentally. A chick was kept on two succeeding 

 nights, from 8 o'clock P. M. till 8 A. M. in an atmosphere con- 

 taining amyl nitrite (which lowers the blood-pressure). 1 This 

 bird later showed two emphasized defective areas in the region of 

 the feather produced during the two days of the experiment, and 

 these areas occupied the region normal to the defective lines and 



1 The effect of several drugs on the blood-pressure of birds has been investigated 

 by Dr. S. A. Matthews and the writer. Our results are soon to be published. 



