356 oscar riddle. 



The Meaning and Cause of Fault-Bars and Funda- 

 mental Bars. 



The facts bearing on fault-bars and, indeed, on fundamental 

 bars, have already been stated. It remains only to point out 

 their inter-relation and significance. 



It has been shown that there exists in certain elements of the 

 rapidly growing feather-germ a rhythm of growth which is 

 dependent upon the nutrition. Those parts of the feather which 

 are grown under the poorest nutritive conditions show defects — 

 fault-bars of all grades of imperfection. Those regions of the 

 feather — normally the larger part — which are produced while 

 growth and cell -division are in full swing, form the fundamental 

 bars. 



In* pigmented feathers the development of pigment is modified 

 at night along with the other elements and there results a 

 structurally weakened and less pigmented area. This region we 

 have thus far spoken of as a fault-bar ; since, however, this same 

 area has been found in some cases to lose considerable pigment 

 without having lost any barbules, we speak of it also as a light 

 fundamental bar. On the other hand, pigment develops uninter- 

 ruptedly during those hours of the day when growth is most 

 rapid, and the well-pigmented portion of the feather then laid 

 down forms the dark fundamental bar} 



Fault-bars and fundamental bars are universal in feathers (in 

 white feathers there is, of course, no rhythm of pigmentation), 

 and are direct expressions of the rhythmic nutritive 2 conditions. 

 The poorest food conditions obtain at night. A reduced blood 

 pressure, probably much emphasized in the later hours of the 

 night is to be regarded as a factor (by affecting the nutrition) in 



1 This is a complete confirmation of a view arrived at by Professor Whitman in 

 1903 (not published until 1 907). From observations quite different from these, he 

 had reason to believe that the bars might be "zones of daily growth (light == day ; 

 dark= night, or vice versa)." 



2 The words " food" and "nutrition" are used in a general sense and include 

 oxygen. It is not improbable that the slower growth and cell division and the diminu- 

 tion of the production of melanin pigment under fault-bar producing conditions are, 

 in part at least, due to a reduced oxygen supply. In all my experiments, and in 

 every lowering of the blood pressure, the oxygen supply of the tissues is diminished. 

 The probability here stated grows in importance when it is remembered that free 

 oxygen plays an important role in the germination of seeds, the segmentation of ova 

 (mitotic activities), and probably also in the oxidation (Samuely) of tyrosin (Ges- 

 sard, v. Ftirth and Schneider) to form melanin. 



