250 A Manual of Veterinary Physiology. 



contractions are much slower and longer. The intestinal 

 movements seen in a horse recently destroyed exhibit per- 

 fectly the latent period, the stage of contraction, and that 

 of relaxation. If the bowels or stomach be very irritable 

 the lightest touch provokes a contraction, and in the case 

 of the stomach particularly, large weals occur on its 

 surface by lightly drawing the finger over it. 



The Elasticity in muscle depends upon its condition. In 

 a resting muscle the elasticity is small but perfect — that is 

 to say, on being stretched it regains its natural length 

 when released ; a working muscle owing to fatigue is less 

 elastic than a resting one. The great advantage to the 

 animal machine of the elasticity of muscles, is the reduction 

 in concussion to the skeleton during progression. The 

 skeletal muscles in the living body are always slightly on 

 the stretch, at any rate they are not slack, as otherwise 

 great loss of time would occur before they could act. 



We have certain muscles in the machine where the 

 strain on them is so considerable that tendinous material 

 is intimately mixed up with the muscular tissue : this is 

 well seen in the masseters, the muscles of the back, fore- 

 arm, and thigh. In the living animal provision is made for 

 the muscles of the limbs being rested without necessitating 

 the horse assuming a recumbent position, viz., by means of 

 the check ligaments in the leg ; by this means a horse 

 can sleep standing, and may remain standing for many 

 weeks without suffering. 



Muscle Fatigue. — Fatigue in muscle is due to excess of 

 work; the products arising from muscular contraction 

 accumulate faster than they can escape, the irritability of 

 the muscles decreases, and they require a greater stimulus 

 to induce them to respond. The fatigued muscles are also 

 acid from sarcolactic acid, which probably produces the 

 soreness and stiffness resulting from overwork. Hand-rub- 

 bing and shampooing the tired body muscles, such as is 

 practised on both man and horse in India, and followed by 

 such good results, is explained by the fact that the lymph 

 vessels are stimulated to further absorption, and the lactic 

 acid and other fatigue products got rid of. This is also 



