56 



ANATOMY FOR NURSES. 



[Chap. VI. 



Numerous nerves are supplied to non-striated muscular tissue, 

 and many blood-vessels. 



The contraction of this kind of muscular tissue is much 

 slower and lasts longer than the contrac- 

 tion of the striated variety. As a general 

 rule the muscles of the skeleton are thrown 

 into contraction only by nervous impulses 

 reaching them along their nerves ; sponta- 

 neous contractions, as in a case of "cramps," 

 being rare and abnormal. The plain mus- 

 cular tissue of the internal organs, however, 

 very often contracts indejiendently of the 

 central nervous system, and under favor- 

 able circumstances will continue to do so 

 after the viscera have been removed from 

 the body. 



The great increase in the muscular tissue of the 

 uterus during gestation takes place both by elonga- 

 tion and thickening of the pre-existing fibre-cells, 

 Fig. 54.— Fibre-cells and also, it is thought, by the development of new 



OF Plain Muscular fibre-cells from small granular cells lying in the 

 TissuK. Highly magni- ^ , , . , . , , ^ 



gg(j tissue. In the shrinking oi the uterus after par- 



turition the fibre-cells diminish to their previous 

 size ; many of them become filled with fat granules, and eventually many 

 are, doubtless, removed by al)sorption. 



Development of striated muscular tissue. — When the muscular fibres 

 are about to be formed, the cells set apart for this purpose elongate, and 

 their nuclei multiply, so that each cell is converted into a long, multi- 

 nucleated protoplasmic fibre. At first the substance of the fibre is not 

 striated, but presently it becomes longitudinally striated along one side, 

 and about the same time a delicate membrane, the sarcolemma, may be 

 discovered bounding the fibre ; then transverse striation commences, and 

 gradually extends around the fibre, and, finally, the nuclei take up their 

 position under the sarcolemma. 



Regeneration of muscular tissue. — It was formerly thought that after 

 removal, by tlie knife, or by disease, muscular tissue was not regenerated, 

 but that any breach of continuity which might occur in the muscle was filled 

 up by a growth of connective tissue. It would appear, however, that the 

 breach is after a certain lapse of time bridged across by muscular substance, 

 but how the new muscular tissue is formed is not fully understood. 



Attachment of muscles to the skeleton. — The muscles are sepa- 

 rate organs, each muscle having its own sheath of connective 

 tissue. The connective tissue extends also into the muscle, form- 



