342 OSCAR RIDDLE. 



Both the arterioles and veins of the comb, wattles, patagium, etc., 

 are dilated. The strongest action, however, is exercised here as in 

 mammals l upon the vessels of the viscera. This was ascertained 

 by making considerable incisions through the body-wall so as to 

 allow free observation ; this was quickly followed by giving the 

 drug. In other cases the bird was anaesthetized with ether before 

 exposure of the viscera. The action of several drugs on the 

 blood-pressure of birds has been studied by Dr. S. A. Matthews 

 and the writer. 2 One of our tracings, showing the effects of amyl 

 nitrite on the vascular pressure of a duck, is shown in text Fig. 

 5. A glance at this figure is sufficient to convince one that the 



AMYL NITRITE 

 NORMAL 



BASE LINE 



Fig. 4. Blood pressure tracing from the carotid artery of a duck. A normal pres- 

 sure of 164 mm. Hg is here recorded. Amyl nitrite was given at a and again at b. 

 The tracing shows a rapid fall in the arterial pressure to 50 mm. Hg. 



alleged powers of amyl nitrite to diminish blood pressure is no 

 myth. 



To test directly the efficacy of amyl nitrite in the production 

 of fault-bars the experiment was carried out in the following way : 

 Two Plymouth Rock chicks of equal age (7 months) were taken 

 at the time of their first moult ; on the evening of the first ex- 

 periment the distal ends of a number of their freshly expanding 

 feathers were measured and very carefully cut away at a distance 



1 Cushny, C. A., " Pharmacology and Therapeutics," p. 470, Philadelphia, 1899. 

 2 Riddle, O., and Matthews, S. A., "The Blood Pressures of Birds and Their 

 Modification by Drugs," Amer. Jour, of Physiol., Vol. XIX., June, 1907. 



