444 VETERINARY PHYSIOLOGY 



(2) Does the wave fall slowly or rapidly ? Normally the 

 fall should not be so sudden as the ascent. When the 

 aortic valves are incompetent the descent becomes very 

 rapid (p. 410) in the so-called " water-hammer " pulse. 



(3) Are there any secondary waves to be observed ? 

 The only one of these which can be detected by the finger is 

 the dicrotic wave, and this only when it is well marked. 

 When it can be felt, the pulse is said to be dicrotic, and, as 

 before stated, this indicates an actively contracting heart 

 with an arterial pressure low relatively to the strength of the 

 ventricles (p. 441). 



2. The Capillary Pulse. 



For the reasons already given, there is normally no pulse 

 in the capillaries (p. 434). If, however, the arterioles to a 

 district are freely dilated, so that little resistance is offered 

 to the escape of blood from the arteries, and if, at the same 

 time, the outflow from the capillaries is not proportionately 

 increased, intermittent inflow and resistance to outflow are 

 developed, and a pulse is produced. Such a condition is 

 seen in certain glands during activity. 



3. The Venous Pulse. 



1. The absence of a general venous pulse has been 

 already explained. But just as in the capillaries, so in the 

 veins, a local pulse may develop. 



2. In the veins entering the auricles and in the veins at 

 the root of the neck a pulse occurs. This may be recorded 

 by means of M'Kenzie's polygraph which consists of a small 

 metal cup connected with a recording tambour. The cup 

 is applied closely to the skin over the vein. This pulse 

 has no resemblance to the arterial pulse, although depending 

 on the same three factors. 



Its form is indicated in fig. 187. 

 Its features are to be explained as follows : — 

 (a) Normal. — Blood is constantly flowing into the great 

 veins, pressed on from behind, (i.) When the auricles con- 

 tract, the outflow from these veins into the heart is suddenly 



