PULMONARY AND SYSTEMIC CAPILLARIES. 



371 



may not be so with tracings taken at a different time ; for while 

 these were being taken, the instrument remained attached to 

 the arm of the patient, and the pressure of the spring which 

 rested upon the artery remained unaltered. In the normal con- 

 dition of the patient, his pulse presented the characters seen in 

 Fig. 149. 



Fig. 149. 



During the attack of angina, the capillaries become con- 

 tracted, and the arterial tension rose as seen in Fig. 150. When 



Fig. 150. 



the nitrite was inhaled, the pulse in most cases quickly regained 

 its normal character ; but when the pain remained in the region 

 of the right nipple after the inhalation, the arterial tension fell 

 as usual, indicating dilatation of the systemic capillaries, but the 

 volume of the pulse remained small, as shown in Fig. 151. The 



Fig. 151. 



small volume is, I think, due to the pulmonary capillaries not 

 dilating, or only imperfectly, under the action of the nitrite ; 

 and if I discontinued the inhalation before the volume of the 



