318 Physiological Action of the Parajfinic Nitrites. [Mar. 5, 



taken of the pulse-rate, after inhalation of a known quantity of 

 nitrite. A mask inhaler was specially devised, so as to avoid loss of 

 substance daring inhalation. It consisted of a conical metal box 

 covering the month, and fitting accurately on the bridge of the nose 

 by the aid of a hollow rubber border, which could be distended by 

 injection of air. It is provided with three tubes opening out of a 

 common trunk in the front of the mask ; one of these was not fur- 

 nished with any valve, but the two lateral tubes had each one valve, 

 opening inwards and outwards respectively. The tube intended for 

 the inspiration of nitrite had a continuation of india-rubber, in the 

 middle of which a glass bulb was inserted for the reception of the 

 nitrite. Spring clamps were placed on either side of the bulb. The 

 mask having been adjusted to the face, and respiration being regular 

 through the valvular tube, the drum was started at full speed so as to 

 record the normal pulse rate, and the inhalation tube was opened by 

 removing the clamps on either side of the bulb at the same time as 

 the interior tube was closed. The time of inhalation was recorded by 

 a signal marker. 



There is a considerable variation on the part of individuals to 

 nitrite effect, the acceleration of the pulse in the case of those of 

 neurotic tendency being much greater, and the time of its con- 

 tinuance much less than in that of a lymphatic subject. The order 

 of activity (extent of acceleration) for various nitrites deduced from 

 a large number of experiments is (1) a-amyl ; (2) /J-amyl ; (3) iso- 

 butyl ; (4) secondary butyl ; (5) primary butyl ; (6) secondary propyl ; 

 (7) primary propyl; (8) ethyl ; (9) methyl. 



The action of each paraffinic nitrite has been closely contrasted with 

 that of amyl nitrite. The results may be broadly summarised as 

 follows : 



All the nitrites examined produce, in whatever way administered, 

 a reduction of blood pressure, variable, however, according to the 

 compound employed in its extent and in its progress, as well as in the 

 ensuing recovery. 



A pulse acceleration usually accompanies and succeeds the fall 

 upon inhalation, the extent of inhalation varying in the case of indi- 

 vidual nitrites. The acceleration is less upon intra-vascnlar injection, 

 especially intra-arterial injection, than when administration is by 

 inhalation ; a distinct retardation of pulse is frequently produced by 

 the former method, especially by carotid injection. 



The extent of acceleration appears to be less in the case of cats than 

 in the human subject. 



The respiration is affected (1) temporarily during and immediately 

 subsequent to inhalation, in various degrees by the different nitrites, 

 and (2) permanently by the repeated administrations of the same or 

 different nitrites. 



