268 VETERINARY PHYSIOLOGY 



On the other hand, if the ventricles are acting slowly and 

 feebly in relationship to the arterial pressure, the initial out- 

 flow of blood does not take place so rapidly and completely 

 (fig. 124, continuous line), and the initial rise in the pulse 

 is thus not so rapid. The residual outflow of blood is more 

 marked and causes a well-marked secondary rise in the pulse 

 curve the predicrotic wave. In certain cases this may be 

 higher than the primary crest, producing the condition known 

 as the anacrotic pulse. The relatively high intra-arterial 

 pressure here prevents the development of a well-marked 

 dicrotic wave. 



In extreme cases of this kind, when the arterial walls are 

 very tense, they may recover after their expansion in an 

 irregular jerky manner, and may give rise to a series of kata- 

 crotic crests producing ;i poly erotic pulse (fig. 123, 3). 



From what has been said it will be seen that a study of 

 the pulse wave gives most valuable information as regards 

 the state of the circulation, and the physician constantly 

 makes use of the pulse in diagnosis. 



Palpation of Pulse. On placing the finger on the radial 

 artery the points to determine are 



1st. The rate of the pulse i.e. the rate of the heart's 

 action. 



2nd. The rhythm of the pulse i.e. of the heart's action as 

 regards (1) Strength of the various beats. Normally the 

 beats differ little from one another in force since the 

 various heart beats have much the same strength. Respira- 

 tion has a slight effect which will afterwards be considered 

 (see p. 321). In pathological conditions great differences in 

 the force of succeeding pulse waves occur. (2) Time relation- 

 ship of beats. Normally the beats follow one another at 

 regular intervals somewhat shorter during inspiration 

 somewhat longer during expiration. In pathological con- 

 ditions great irregularities in this respect may occur. 



3rd. The volume of the pulse wave. Sometimes the wave 

 is high and greatly expands the artery sometimes less high 

 and expanding the artery less. The former condition is called 

 a full pulse (pulsus plenus), the latter a small pulse (pulsus 

 parvus). The fulness of the pulse depends upon two factors : 

 1st. The average tension in the arteries between the pulse beats. 



