142 THE MUSCULAR TISSUE. 



and insertion. The muscles, collectively, form the mus- 

 cular system. They have been arranged under two grand 

 divisions. 



1st. The Voluntary, or all those subject to the control of 

 the will. 2d. The Involuntary, or those over which the 

 will has no influence. A third division is made, called the 

 Mixed class of Muscles, which is a compound of the other 

 two, over which the will has only partial control, as seen 

 in most of the Sphincters. 



The first class are by far the most numerous, and situ- 

 ated chiefly upon the face and extremities composing the 

 greater bulk of the organs of relation. The second class 

 belong to the organs of nutrition, comprising the stomach, 

 intestines, heart, &c. Muscles are either arranged in pairs 

 or are symmetrical. The first are found upon either side 

 of the median line of the body, perfectly distinct, wide 

 apart, and each exactly alike, as upon the limbs; or they 

 may approach so close along the middle line as to touch 

 6ne another, but still preserve their perfect distinctness 

 of separation. The symmetrical muscles are situated pre- 

 cisely upon the median line, and consist in two equal and 

 similar halves. 



Muscles, according to their form, are distinguished into 

 the long, the flat or wide, and the short. The long mus- 

 cles are generally placed upon the limbs, to the beauty 

 and conformation of which they very much contribute. 

 The wide are mostly situated upon the parietes of cavi- 

 ties, as those of the chest and abdomen, and "serve to 

 protect the internal organs, aid their functions, and move 

 the body or the limbs, as the one or the other is the fixed 

 point." The wide muscles, generally, are not very thick 

 in some places resembling a thin membrane, as the broad 

 muscle of the neck, so conspicuous in the horse, which 

 that animal uses as a fly-brusher. The short muscles are 

 commonly met with in parts where there is a limited 

 extent of motion and great power required, as in the 

 movements of the lower jaw and the thumb. The situa- 

 tion of muscles is either superficial or deep. The superfi- 



