534 Caroline McGill. 



these fibrils become coarser, Figs. i7-49. Instead of running 

 straight, as they do in resting nuclei, they may run a wavy course 

 or even tv^rist up into distinct spirals. Figs. 48-49. Finally these 

 chromatin strands collect at the ends of the nuclei and fuse there 

 to form a coarse reticulum, Fig. 51. The chromatin spirals are 

 never as distinctly marked as were those described by Miinch, 1903. 



In the stomach of the chicken the nuclei contract in about the 

 same manner as described for JSTecturus, Figs. 68-72. In the nuclei 

 of the smooth muscle fibers of arteries there are fewer chromatic 

 changes than were observed in other muscle. Figs. 54-64, 77-80. 

 The dark bands shown in Figs. 81-84 are due to folding of the nuclei 

 and not to condensation of the chromatin. 



The whole behavior of the chromatin of the nuclei during con- 

 traction indicates that the contraction of the smooth muscle nucleus 

 is a very active process. It is highly improbable that the changes 

 described could be brought about passively by the contraction of the 

 extra-nuclear portion of the muscle fiber,. 



3. The effect of contraction on the volume of the nucleus. 



An attempt was made to determine by actual measurement 

 whether there is change in the volume of smooth muscle nuclei dur- 

 ing contraction. Not enough data have been obtained to determine 

 the point definitely. From the results at hand it seems that there 

 is no change in the volume during contraction. 



4. The effect of fatigue on the nucleus. 



Gilman, 1903, showed that when striated muscle is completely 

 fatigued the nuclei are shrunken, crenated, more lightly staining 

 and less granular than in muscle not so fatigued. Similar experi- 

 ments were made by the author on smooth muscle. Strips from the 

 muscularis of the intestine of ISTecturus were suspended in a moist 

 chamber, arranged for electrical stimulation, and were stimulated 

 until no further contractions could be obtained. Forty contractions 

 M'a:^ the maximum uumlx-r obtained from one piece. Wlu'ii the 

 strip was completely fatigued, it was fixed and sectioned. The 

 sections were studied, along with like sections from control muscle, 

 for comparison. In none of the material was there any indication 

 of shrinkage or creuation of the nuclei. In every instance the 



