THE MUSCULAH SYSTEM 81 



heat rigor is at once manifest. In both cases, the rigor is due to 

 coagulation of the muscle substance. 



24. Minute Structure of Voluntary or Striped Muxcle. With needles 

 tease out, in normal salt solution, on a glass, a small piece of skeletal 

 muscle of a frog or other animal. Mount and examine with the com- 

 pound microscope. It will be seen to be composed of elongate thread- 

 like bodies, tapering (when not broken) at the ends. Some fibers will 

 show cross markings. 



25. The Minute Structure of Involuntary or Plain Muscle. Tease 

 out, as in the foregoing, a small piece of the outer wall of the intestine 

 of a frog or cat. Here the fibers are seen to be spindle-shaped cells, 

 much shorter than the striped muscle fibers. 



The fibers of both striped and plain muscle can be much more 

 easily teased apart if the tissue be kept in a 20 per cent solution of 

 nitric acid one to two days. 



26. Cross Section of Muscle. Minute Structure. If a prepared 

 cross section of a small skeletal muscle can be obtained, the internal 

 structure of a muscle can be very well shown by aid of the compound 

 microscope. 



27. Minute Structure of Tendon and Ligament. Carefully tease 

 out in normal salt solution, on a slide, a small piece of a thin tendon 

 from the tail of a mouse. To obtain the tendon, cut off the tail from 

 the body, and then pull out the delicate tendinous threads from the 

 cut end. The tendon should be mounted immediately after removal, 

 to avoid drying. A convenient method of mounting is to stretch the 

 tendon across a slide, through a drop of normal salt solution in the 

 center, allowing the ends of the tendon to adhere to the dry edges of 

 the slide. On examining with the compound microscope the tendon 

 is seen to be composed of wavy bundles of fibers. If the preparation 

 be treated with a one per cent solution of acetic acid, the fibers will 

 swell and disappear from view, but there will appear, between the 

 bundles, rows of spindle-shaped cells. 



MACT'S PHYS 



