CHAPTER VI. 

 GENERAL PHYSIOLOGY OF 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 connected 

 with 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 contradistinction to the bones and 

 joints, which are but passive agents in the performance of the corre- 

 sponding 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 stim- 

 ulus transmitted to them from the nervous system. Muscles are 

 divided into: 



1. Voluntary muscles, comprising those the activity of which is 



called forth by an act or effort of volition. 



2. Involuntary muscles, comprising those the activity of which is 



entirely independent of the volition. 



The voluntary muscles are also known from their attachment to 

 the skeleton as skeletal, and from their microscopic appearance as 

 striped or striated muscles. Though for the most part these muscles 

 are red, there are certain muscles in man and other animals which 

 are pale in color. The involuntary muscles, from their relation to the 

 viscera of the body, are known also as visceral, and from their micro- 

 scopic appearance as rjlan^jmooth^- or non-striated muscles. 



THE VOLUNTARY OR SKELETAL 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 



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