84 PRINCIPLES OF VETERINARY SURGERY 



scapula muscles from injury to the supra-scapular nerve, 

 (2) atrophy of the crural muscles following azoturia, (3) 

 atrophy of the caput and adjacent muscles following injuries 

 to the brachial plexus. 



In each of these examples the wasting process is a much 

 more rapid one than inactivity alone could produce. The 

 nutrition as well as the motion of the vapid muscle is un- 

 doubtedly impaired. The almost total disappearance of a 

 muscle within the short space of ten days could hardly be at- 

 tributed solely to motor paralysis in the face of so many in- 

 stances in which muscles remain dormant for weeks with 

 only nominal atrophy. As the result, in each of these atro- 

 phies the cause is peripheral nerve paralysis. Two of them 

 are of traumatic and the other of unknown origin, and in 

 each instance the wasting process is extremely rapid in spite 

 of the fact that the blood supply of the paralyzed muscles is 

 fairly well maintained by the activity of the surrounding 

 muscles. Furthermore the wasting process is not prevented 

 by attempts to excite the circulation of the parts with irri- 

 tants, massage, etc., before the wasting process has begun. 

 From these facts it becomes evident that muscular atrophy is 

 due both to motor and trophic paralysis. 



(2) Inactivity or Disuse. — Unless an organ is in active 

 use it will diminish in volume and even entirely disappear. 

 Organs that are specially concerned in fretal development 

 waste away after birth when they have no further function 

 to perform ; muscles not in active use shrink until only their 

 stroma remains, and in fact every tissue and every organ of 

 the body will enlarge and shrink in strict obedience to its 

 state of activity. This is physiologic atrophy. It 

 is the most common of the wasting processes of 

 animals. Lameness due to diseased processes in the 

 supporting structures of the extremities will cause 

 atrophy of the muscles fai above the seat of dis- 



