MTJSCTJLAK CONTRACTILITY. 461 



muscular efforts. After long-continued exertion, we appre- 

 ciate a sense of fatigue that is peculiar to the muscles. It is 

 difficult to separate this entirely from the sense of nervous 

 exhaustion, but it seems to be, to a certain extent, distinct ; 

 for when suffering from the fatigue that follows over-exer- 

 tion, it seems as though we could send a nervous stimulus to 

 the muscles, to which they are, for the time, unable to 

 respond. When we come to consider fully the subjects of 

 muscular and nervous irritability, we shall see that these 

 two properties are entirely distinct, and that we may ex- 

 haust or destroy the one without influencing the other. 



When the muscles are thrown into spasm or tetanic con- 

 traction, a peculiar sensation is produced, entirely different 

 from painful impressions made upon the ordinary sensitive 

 nerves. In the cramps of cholera, tetanus, or the convul- 

 sions from strychnine, these distressing sensations are very 

 marked. The so-called recurrent sensibility of the anterior 

 roots of the spinal nerves is probably due to the tetanic con- 

 tractions produced by galvanizing these filaments. This 

 question, however, will be taken up again in connection 

 with the nervous system. 



If the muscles possess any general sensibility, it is very 

 faint. A muscle may be lacerated or irritated in any way 

 without producing actual pain, though we always can ap- 

 preciate the contraction produced by irritants, and the sense 

 of tension when the muscles are drawn upon. 



Muscular Contractility, or Irritability. Physiologists 

 now regard muscular irritability as synonymous with con- 

 tractility ; and perhaps the latter term more nearly expresses 

 the fact, though the term irritability, applied to the nerves, 

 and even of late years to the glands, is one very generally used. 



By irritability we understand a property belonging to 

 highly-organized parts, which enables them to perform cer- 

 tain peculiar and characteristic functions in obedience to a 

 proper stimulus. In the sense in which the term is gen- 



