756 



VOLUNTARY MUSCLE. 



of muscles, or injuries, and may occur as one of the sequelae of typhoid 

 fever and diphtheria. 



Hypertrophy. True hypertrophy of muscle as a pathological condition 

 is rare, but it has been described in a few cases. It is usually confined 

 to circumscribed groups of muscles. On microscopical examination the 

 diameter of the fibres is increased, sometimes considerably, though not 

 uniformly. The transverse striatiou is unaltered and the muscle nuclei 

 are in some cases enlarged. The cause of the change is unknown. 



Atrophia Musculorum lipomatosa (Pseudo-hypertrophy of the Muscles). 

 In some cases, haud-in-hand with the production of new connective tissue 

 in the muscles and the atrophy of the muscle fibres, or after these changes 



d. a~ j 

 r <* 





I 



* 













J* I 



FIG. 496. PROGRESSIVE MUSCULAR ATROPHY (Soleus muscle, transverse section). 



o. Increased interstitial tissue; b, nearly normal muscle fibres: c, degenerated muscle fibres; d, atrophied 

 muscle fibres ; e, clusters of proliferated muscle nuclei. 



have made considerable progress, there occurs a development of fat 

 tissue between the fibres (Fig. 497) which may prevent any apparent 

 diminution in the size of the muscles, or in some cases may even give 

 them the appearance of a great increase in size. This condition is of 

 most frequent occurrence in children, and is most apt to appear in the 

 gastrocnemii muscles. In the upper extremities the deltoid and triceps 

 are most frequently involved. The lesion may be symmetrical, affecting 

 similar muscles on both sides of the body, or it may be unilateral. Parts 

 of muscle bellies may be affected. 



The cause of this form of atrophy is not definitely known. Various 

 lesions of the spinal cord have been described as occurring with it ; but, 



