PULSE. 109 



origin in the capillaries, from whence they gradually increase in size, and 

 run into each other, and form larger and larger veins, and ultimately lead 

 into the heart. 



In structure the coats of the veins bear a general resemblance to those 

 of the arteries. They do not, however, possess complete elastic coats. 

 What elastic tissue they have is interwoven in their fibro-cellular tissue, 

 which being in itself extensile and elastic enables them to recover the 

 temporary extensions to which they are liable. The part of their walls 

 which corresponds with the muscular coats of the arteries, is composed of 

 fibres resembling those of fibro-cellular tissue combined with well-marked 

 fibre cells of organic muscle ; by the agency of which the veins probably 

 possess some power of independently contracting on their contents. The 

 coats of the veins are supplied with blood by a system of smaller veins 

 called the venae venarum. 



As a substitute for the strongly developed elastic coats of the arteries, 

 valves are placed in all veins, where they are subject to pressure from 

 the muscles between or near to which they run. These valves prevent 

 any return of the blood, which might otherwise arise from such pressure. 

 In parts, which are not subjected to such pressure, there are no valves. 

 In the foot for instance there are none, and but few in the viscera. 



It is probable that the veins are the principal agents in absorbing the 

 waste and excrementitious parts of the body. 



The Pulse will form the subject of the next chapter. 



CHAPTER 11. 

 THK PULSE. 



210. Importance of the indications of the Pulse. 211 . Cause of pulsation. 

 212. Number of pulsations per minute. 213. Taking the pulse. 214. 

 Irregularities of the pulse. 215. Range of pulse in disease. 216. Auscul- 

 tation as regards the pulse. 217. Action of the "heart. 217 'a. Temperature. 



210. Importance of the indications of the Pulse. 



The Pulse in the horse, as in other animals, is an important guide in 

 determining the healthy state or otherwise 'of the patient. It indicates 

 the number, force, regularity or otherwise of the heart's action, and the 

 quantity of blood sent forth at each beat. 



In examining the pulse, the characters to be especially noticed are its 

 frequency, regularity, and compressibility. As a general rule, the num- 

 ber of the pulse corresponds with the heart's contractions. In certain 

 cases, however, of heart disease, the impulse is not conveyed far on 

 account of the ventricles receiving only a small quantity of blood. 



