(, Continued from preceding page.) 

 long, rodlike structures with delicate chromatin reticulum (r. nu.). In the 

 contraction nodes they are shorter and thicker with the deeply staining 

 chromatin massed at the ends (c. nu. ). Zenker's fluid. Hansen's h:Teniatoxylln- 

 eosin. x 1'''<jO. 



Fig. 23. A contracted portion of the circular coat of the small intestine of 

 Necturus, contracted by electrical stimulation. In the contraction wave the 

 fibers stain deeply with the hjematoxylin, the nuclei are short and thick with 

 the chromatin massed at the ends, the connective tissue is condensed — c. n., 

 conti-actiou node ; i. c, interstitial connective tissue ; f. mf., fine myoflbrilhp ; 

 c. nu., contracted nucleus with coarse chromatin reticulum. Zenker's fluid. 

 Iron-htematoxylin-eosin. X 880. 



Fig. 24. An uncontracted portion of the circular muscle coat taken from 

 the same section and magnified the same amount as Fig. 23, showing the 

 structure of the relaxed muscle, r. nu.. resting nucleus with fine chromatin 

 reticulum ; fmf., fine myofibrilhie ; cf., fine collagenous fibers. Zenker's fluid. 

 Iron-hsematoxylin-eosin. x 880. 



Fig. 25. Cross-section of a portion of the longitudinal muscle coat of 

 intestine of Necturus, muscle contracted — c. n., contraction node ; i. s., inter- 

 nodal segment showing myofibrillre ; p. nu., a muscle fiber with the nucleus 

 at the periphery ; c. nu., contracted nucleus : i. c, interstitial connective tissue. 

 Zenker's fluid. Iron-hjematoxylin-eosin. X §80. 



Fig. 26. Cross-section of uncontracted muscle taken from the same section 

 as Fig. 25 and drawn to the same scale. When Figs. 25 and 26 are compared 

 the marked thickening of both fibers and nuclei during contraction is very 

 apparent — r. nu., resting nucleus. Zenker's fluid. Iron-haematoxylin-eosin. 

 X 880. 



