CIRCULATORY SYSTEM. U''3 



which has its origin in its very centre. Its fleshy belly crosses ob- 

 liquely over to the inner part of the leg, where it terminates, mid- 

 way between the stifle and hock, in its cordiform tendon, which 

 passes through a theca at the inner side of the hock. Opposite to 

 the head of the gieat metatarsal bone it runs in the same sheath 

 with the tendon of the flexor pedis, with which it ultimately forms 

 one common tendon. 



Action. — It operates as a coadjutor to the flexor pedis. 



Section III. 

 CIRCULATORY SYSTEM. 



THE CIRCULATORY SYSTEM COMPRISES THE BLOOD, THE 

 BLOODVESSELS, AND THE HEART, 



OF THE BLOOD. 



BLOOD is the red fluid we see issuing from a fresh wound, 

 and of which there is a considerable quantity continually circu- 

 lating through the body of a living animal. So uniform is it, while 

 circulating, in its appearance, that it looks like a simple, uncora- 

 pounded, or homogeneous fluid ; a 'character it does not lose until 

 some time after it has been drawn out of the body, and then it 

 gradually assumes a change from a fluid into a solid mass, resem- 

 bling jelly. In the fluid state it possesses a faint odour, a saline 

 flavour, has an adhesive unctuous feel, and is some little (speci- 

 fically) heavier than water : the latter being equal to 1000, blood 

 may be estimated at 1090. Also, so long as it continues tepid, it is 

 perceived to emit from its furface a halitus, or vapour • which is 

 nothing more than ordinary steam, excepting that the evaporation 

 may carry up with it minute particles of animal matter : a circum- 

 stance that will accountfor the peculiar odour it is known to convey. 



It has been observed that blood, soon after its removal from 

 the body, concretes into a solid gelatinous mass. This spontane- 

 ous change, called the coagulation, proceeds very gradually to 

 completion, until we discover the formation of two very different 

 component parts : one solid, denominated the clot, ox crassamoi- 

 liim ; the other fluid, named the serum. Simple concretion takes 

 place in the blood of the horse in about twenty-five minutes : in 

 that of a man it requires only seven. The relative proportions of 

 the crassamentum and serum (when the coagulation is finally com- 

 pleted) will be found to vary in the blood of difTerent animals, and 

 that even of the same animal at difterent periods, depending on 

 the state of health and condition of the subject from which it is 

 drawn. In man, the crassamentum may be said to amount to about 



