172 OSCAR RIDDLE. 



juvenal plumage in great numbers. The same experiment was 

 tried on young chicks with the same result. It was noticed, 

 however, that notwithstanding the careful and plentiful feeding of 

 the control, an occasional defect could be found in their feathers 

 too. These experiments l showed that malnutrition is beyond 

 doubt the important factor in the production of the defective 

 areas, but apparently not the only one. An experiment was then 

 carried through to learn whether the defects found in the control 

 could be produced by the usual handling, of the birds, and per- 

 haps slightly crumpling their feather-germs. The results were 

 negative ; but it was found that when the feather-germs were 

 strongly cm inpled and broken in the region of feather growth, the 

 defects were readily produced. 



During the progress of an experiment on some young chicks 

 (carried on for a quite different purpose) it was found that chicks 

 which were fed on the fat stain Sudan III produced the defective 

 areas in much greater numbers than did the control birds. It 

 was determined that the ordinary variations of light, temperature, 

 etc., did not cause the defects. The net result so far of all the 

 experiments for the determination of the cause of the defects, 

 indicated that those things which interfere with the nutrition of 

 the feather-germ will produce the defects, while those things not 

 capable of affecting the nutrition will not produce them. It is 

 easy to understand how a crumpling of the feather-germ would 

 temporarily interfere with the circulation within it. In the chicks 

 fed with Sudan III. it was evident that a sort of " starving " 

 effect was produced by it. By the time the experiments had 

 proceeded thus far I knew that a day of normal growth in a 

 feather is represented by a "fundamental bar" and a defective 

 line, and also that a defective line stands in close relation to a de- 

 fective area. This suggested that the defective areas in the con- 

 trol, and the defective lines in all feathers, are produced by an 

 internal factor with a definite rhythm, and that the rhythm is able, 

 like my experiments, to effect the nutrition of the feather ele- 

 ments. This recommended blood-pressure to me, and the ex- 

 periments were made with the result stated above. 



Blood-Pressure and Temperature Rhythms. - - 1 shall not here 



1 Partial results of these feeding experiments were communicated by letter to 

 Professor Duerden and were published in his paper, cited elsewhere. 



