64 MEDICINES ACTING ON MUSCLE 



experimentally by washing out the muscle with a current 

 of blood or serum, either of which supplies it with food at 

 the same time, or with normal saline solution containing a 

 trace of alkali. In practice, removal of these waste pro- 

 ducts is hastened by shampooing the muscles, or massage, 

 the effects of which, in overcoming fatigue, are fully recog- 

 nised. In like manner thorough grooming and diligent 

 hand-rubbing of the limbs of horses after hard work lessen 

 fatigue, and prevent subsequent stiffness and swelling of 

 joints. 



But muscle fibres are susceptible to other stimuli than 

 impulses along the motor nerves, for thermal or electrical 

 stimulation will cause contraction even when all the nerve 

 fibres in the muscle have been destroyed. Similarly, drugs 

 can affect the muscle fibres themselves, some stimulating to 

 stronger and quicker contraction, others depressing, lessen- 

 ing the power of contraction, and making the reaction 

 slower. 



Muscular spasms consist of irregular purposeless con- 

 tractions of either voluntary or involuntary muscles, 

 usually depending on faulty action of the higher co-ordin- 

 ating centres. They may, however, be due to some change 

 in the muscle itself, or to the direct action of some poison. 

 Spasms may be either tonic, as in tetanus of muscle, or 

 clonic, as in tremor or rigors. Spasm of involuntary 

 muscles, as illustrated by that of the blood-vessels, bronchi, 

 or intestines, is antagonised by nitrites, such as amyl-ni trite 

 and nitrous ether (see Antispasmodics). When a muscle, or 

 its motor nerve, receives an abnormal number of stimuli, 

 so that it has no time to relax between them, instead of 

 contraction being followed by relaxation, prolonged tonic 

 contraction or tetanus ensues. This occurs with poisons 

 like strychnine and with tetano-toxin. 



' Rapid alternation of contraction and relaxation, or 

 tremor, may affect either (a) a few bundles of muscular 

 fibres ; (6) a single muscle ; or (c) groups of muscles ' 

 (Brunton). Such tremor may occur when the muscle is at 

 rest, or when it is in motion. This form of insubordination 

 may probably result from the number of stimuli from the 

 nerve-centre being either too few or too many. 



