GENESIS OF FAULT-BARS IN FEATHERS. 343 



of 18 mm. from the skin. At 8:00 P. M. the birds were brought 

 into the laboratory and were placed in similar large glass jars ; a 

 tube of amyl nitrite was broken in a bottle , the bottle was par- 

 tially stoppered and placed in the jar with chick No. 1 ; the dose 

 was regulated by means of the stopper ; the comb and patagium 

 serving as indicators. On the first night, however, in order to 

 make sure that it was effective, the dose was increased until the 

 bird toppled over unconscious ; the bird was taken out and re- 

 vived, replaced, and the supply of amyl nitrite slightly reduced. 

 The bird now showed no discomfort, but chuckled and sang as if 

 to express satisfaction; the birds were observed until 12 P. M. 

 At 8:00 A. M. they were both released, returned to the green- 

 house and fed as usual ; at 8:00 P. M. of the same day they were 

 again brought into the laboratory and the procedure of the pre- 

 vious evening repeated ; at this time, however, No. 1 was not 

 given sufficient of the drug to produce unconsciousness ; on the 

 following day at 8:00 A. M. they were again returned to the 

 green-house ; measurements of the rate of growth of some of 

 their marked feathers were taken at intervals of two or three days 

 during the next two weeks ; feathers for sectioning were removed 

 from birds I. and II. before the experiment began, and on the 

 mornings following each experiment. 



The result of this experiment leaves, I think, no room for 

 doubt on one or two important points. When the parts of the 

 feathers grown during the two days of the experiment had ex- 

 panded, it was found that in No. 1, two pronounced defects (PI. 

 XIV., Figs. 22-23) had been produced. The feathers of No. II. 

 were normal (PI. XIV., Fig. 24). The sections tell the same 

 story. The longitudinal section of a feather-germ (PL XV., Fig. 

 25) taken from the bird on the morning after the first experi- 

 ment shows an abnormal region at about 2.5 mm. from the end 

 of the feather. This undoubtedly represents the fault-bar pro- 

 duced on the preceding night. 



There can be no question that amyl nitrite, when used as out- 

 lined above, is able to produce fault-bars in chicks. The ques- 

 tion may of course be raised as to whether it does so by lower- 

 ing the blood pressure or by some other means. In my opinion 

 the probabilities that it does so are overwhelming, though its 



