THE MUSCULAR SYSTEM 305 



usually recommended that the horse be placed on a mash diet, and have a 

 dose of purgative medicine administered to him, and that afterwards he be 

 blistered once or twice and have a long rest not less than two months. 

 The general result of such a course of procedure is that the animal comes 

 up much improved. He is put to work, which, if hard, in the course of 

 two or three months causes his legs again to become as bad as ever. Still 

 he is worked on, until finally he is permanently bowed at the knees, not 

 being able, as when at first affected, to stand at times upright. 



The impediment now consists in a slight thickening and consequent 

 shortening of the ligamentous tissue we have before referred to. 



No treatment in this advanced stage would be of any avail, whether 

 medicinal, surgical, or mechanical. Such a horse must be considered as 

 unsound, if the affection exist in more than a slight degree; for although 

 we daily observe horses thus deformed doing their work well, still, on the 

 other hand, many of them show blemished knees, the result of falls. 



17. THE MUSCULAR SYSTEM 



There are two kinds of muscle, distinguished as striated or voluntary 

 and non-striated or involuntary. 



Striated muscle is red in colour, and forms nearly one-half of the 

 entire weight of the body. It clothes the bones of the skeleton and 

 moves them in obedience to the will, hence the term " voluntary " muscle. 



A voluntary muscle consists of an aggregation of bundles of fibres 

 united by connective tissue in which blood-vessels and nerves ramify 

 to nourish and innervate them. 



A muscle fibre, as seen under the microscope, is a minute, pale, faintly 

 yellow filament. It is composed of an outer sheath or sarcolemma, within 

 which is contained a contractile substance. 



The sheath is a very thin, transparent, structureless membrane. It 

 possesses no power to contract, but, being elastic, is capable of accommo- 

 dating itself to the necessary changes which its contents undergo. 



The contractile substance enclosed in the sarcolemma consists of a 

 number of delicate filaments placed side by side, termed JibrillcB. Each 

 fibrilla is composed of a chain of minute bodies called sarcous elements. 



These are united in such a way as to give the fibre a succession 

 of transverse markings, hence the term striated muscle; other but less 

 distinct striations occur along its length, as a result of the contact of the 

 several fibrillae. 



VOL. II. 54 



