CHAPTER VII 

 GENERAL PHYSIOLOGY OF MUSCLE-TISSUE 



The Muscle-tissue. The muscle-tissue, which closely invests the 

 bones of the body and which is familiar to all as the flesh of animals, is the 

 immediate cause of the active movements of the body. This tissue is grouped 

 in masses of varying size and shape, which are technically known as muscles. 

 The majority of the muscles of the body are attached to the bones of the 

 skeleton in such a manner that, by an alteration in their form, they can 

 change not only the position of the bones with reference to one another, but 

 can also change the individual's relation to surrounding objects. They are 

 therefore, the active organs of both motion and locomotion, in contradistinc- 

 tion to the bones and joints, which are but passive agents in the performance 

 of the corresponding movements. In addition to the muscle masses which 

 are attached to the skeleton, there are also other collections of muscle- 

 tissue surrounding cavities such as the stomach, intestine, blood-vessels, etc., 

 which impart to their walls motility, and so influence the passage of material 

 through them. 



Muscles produce movement of the structures to which they are attached 

 by the property with which they are endowed of changing their shape, 

 shortening or contracting under the influence of a stimulus transmitted to 

 them from the nerve system. Muscles are divided into: 



1. Skeletal muscles, comprising those muscles which are attached to the 

 various bones of the skeleton. 



2. Visceral muscles, comprising those muscles which are found in and 

 which compose a portion of the walls of the hollow viscera and 

 blood-vessels. 



As the skeletal muscles are capable of being excited to activity by nerve 

 impulses descending from the cerebrum as a result of volition they are 

 frequently termed voluntary muscles. By reason of their appearance as 

 seen under the microscope they are termed also striped or striated muscles. 

 As the visceral muscles are not capable of being excited to action by volition 

 they are frequently termed involuntary muscles. By reason of their ap- 

 pearance as seen under the microscope they are termed also non-striated 

 or smooth muscles. 



Though for the most part the skeletal muscles are red in color, there are 

 certain muscles in man and other animals which are pale in color and in 

 many muscles, pale fibers are extensively distributed among the red fibers. 



THE SKELETAL OR VOLUNTARY MUSCLE 



All skeletal muscles consist of a central fleshy portion, the body or belly, 

 provided at either extremity with a tendon in the form of a cord or mem- 

 brane. The body is the active, contractile region, the source of the move- 

 Si 



