VERTEBRATE MUSCLE TISSUES 1 



1. Unstriated Muscle. Examine, with the low and high power, a pre- 

 pared transverse section of frog intestine. Note that it is composed of 

 a number of layers as follows : (a) the thin, outer covering (peritoneum) ; 

 (b) the muscular layers consisting of an outer longitudinal layer and 

 a thicker, inner circular layer; (c) the connective tissue layer (sub- 

 mucosa), and (d) the epithelial layer (mucosa) which is thrown into folds, 

 and forms the inner lining of the intestine. 



2. Study the two layers of unstriated muscle tissue under the high 

 power. Note that the tissue of the circular layer consists of closely 

 packed, elongated, spindle-shaped cells. In the longitudinal layer this 

 same type of muscle is also present, but in this case the cells have been 

 cut transversely so that the true shape of the cell bodies is not seen. Draw 

 a portion of both layers to show the structure as observed. 



3. Examine a small piece of tissue from the wall of frog intestine or of 

 bladder, which has been properly macerated so as to show the spindle- 

 shaped unstriated muscle cells separated from each other. Note the 

 structure of the individual cells, each with a distinct nucleus and very 

 delicate longitudinal striations. Draw several cells to show structure as 

 observed. 



4. Striated Muscle. Place a small piece of fresh muscle from the leg 

 of a Frog in a drop of normal salt solution on a slide. Tear it thoroughly 

 apart with dissecting needles. Add a drop of acetic carmine stain, mount, 

 and examine with the low and the high power. Note that this type of 

 tissue consists of long, striated, cylindrical bundles of muscle fibers 

 bound together by connective tissue (perimysium) . Under the high power 

 study the cytoplasm (sarcoplasm) of the muscle fibers and observe the 

 distinct transverse striations and the less distinct longitudinal stri- 

 ations which are present in them. Each tiny fiber represents a single 

 modified, multinucleate cell with several nuclei embedded in the sarco- 

 plasm. A very thin layer of connective tissue (sarcolemma) encloses 

 each fiber. Draw to show the structure as observed. 



i B. pp. 169-172. 



317 



