VARIABILITY OF THE MUSCULAR SYSTEM. 



97 



tlie contractile substance diminishes in length, and is re- 

 placed by tendon, which often assumes a considerable develop- 

 ment. 



J. Guerin, when pointing out the fibrous degeneration of 

 the muscles, thought that he saw in it the proof of a primi- 

 tive muscular retraction, which would ultimately have pro- 

 duced dislocation of the foot. This eminent surgeon also 

 thought that the alteration of the fibre was the only lesion of 

 the muscles in club-foot. Scarpa maintained, on the contrary, 

 that in the greater number of cases the luxation of the foot 

 was the original phenomenon. 



As to the nature of muscular change, all surgeons at present 

 agree in admitting that it may have two difierent forms, and 

 that sometimes the muscle undergoes fatty degeneration, and 

 in other cases it is transformed into fibrous tissue. We are 

 especially indebted to the beautiful works of Cuvier, for our 

 knowledge of the conditions under which each of those 

 changes in the muscular substance is produced. 



An example will illustrate how the muscles are afiected 

 Recording as their function is suppressed, or simply limited 

 in extent. 



The muscles of the calf of the leg, or gastrocnemians, are 

 two in number ; their attachments and their functions are 

 very difierent. Both are inserted below in the calcaneum, by 

 the tendon of Achilles, and are, consequently, extensors of the 

 foot on the leg. But their superior insertions are different ; 

 the soleus, having its insertion exclusively in the bones of the 

 leg, has no other office than that of extending the foot, as we 

 have said before. The twin gastrocnemii, on the contrary, 

 being inserted in the femur, above the condyles of that bone, 

 have a second function, that of bending the leg upon the 

 thigh. 



Let us suppose that anchylosis of the foot has been pro- 

 duced ; it entirely suppresses the function of the soleus, which 

 passes through the fatty degeneration, and disappears. The 

 two gastrocnemii are in a different condition ; if their action 

 on the foot has ceased, there still remains their function of 

 bending the leg on the thigh ; these muscles have, therefore, 

 only one of their movements reduced in amplitude. Con- 



