138 THE HUMAN BODY. 



There seems in fact to be some connection between that ar- 

 rangement of the contractile substance which shows itself 

 under the microscope as striation and the power of rapid 

 contraction, since we find that the heart, which is not a 

 skeletal or voluntary muscle but yet one that contracts rap- 

 idly, agrees with these in having its fibres striated. 



Hygiene of the Muscles. The healthy working of the 

 muscles needs of course a healthy state of the Body gener- 

 ally, so that they shall be supplied with proper materials- 

 for growth and repair and have their wastes rapidly and 

 efficiently removed. In other words, good food and pure 

 air arc necessary for a vigorous muscular system, a fact 

 which trainers recognize in insisting upon a strict dietary, 

 and in supervising generally the mode of life of those who 

 are to engage in athletic contests. The muscles should also 

 not bo exposed to any considerable continued pressure since 

 this interferes with the flow of blood and lymph through 

 them. 



As far as the muscles themselves are directly concerned, 

 exercise is the necessary condition of their best develop- 

 ment. A muscle which is permanently unused degenerates 

 and is absorbed, little finally being left but the connective 

 tissue of the organ and a few muscle fibres filled with oil- 

 drops. This is well seen in cases of paralysis dependent 

 on injury to the nerves. In such cases the muscles may 

 themselves be perfectly healthy at first, but lying unused 

 for weeks they rapidly alter and, finally, when the nervous, 

 injury has been healed, the muscles may be found incapa- 

 ble of functional activity. The physician therefore is often 

 careful to avoid this by exercising the paralyzed muscles 

 daily by means of electrical shocks sent through the part. 

 The same fact is illustrated by the feeble and wasted condi- 

 tion of the muscles of a limb which has been kept for some 

 time in splints. After the latter have been removed it is 

 only slowly, by judicious and persistent exercise, that the 

 long idle muscles regain their former size and power. The 

 great muscles of the "brawny arm" of the blacksmith or 

 wrestler illustrate the reverse fact, the growth of the mus- 

 cles by exercise. Exercise, however, must be judicious; re- 



