532 Caroline McGill. 



Figs. 27-29 and 85-89 show two series of nuclei from the smooth 

 muscle of the intestine of Necturus, which illustrate well the de- 

 crease in length and increase in thickness which occurs during con- 

 traction. The following measurements taken from nuclei of both 

 contracted and uncontracted smooth muscle of Necturus, serve as 

 further illustration of the point in question: 



Length of Nucleus. Greatest Width of Nucleus. 



No. 1 82 micra 5 micra 



No. 2 72 micra 8 micra 



No. 3 62 micra 9 micra 



No. 4 55 micra 9 micra 



No. 5 43 micra 10 micra 



No. 6 35 micra 15 micra 



No. 7 30 micra 17 micra 



No. 8 29 micra 16 micra 



No. 9 28 micra 18 micra 



Figs. 42-53 is a similar series from the smooth muscle of the 

 large intestine of dog, Figs. 55-58 from a small artery from the 

 mesentery of pig, Figs. 65-67 from the bladder of cat. Figs. 68-72 

 from the muscular stomach of chicken, and Figs. 77-80 from the 

 carotid artery of ox. 



During contraction the nucleus changes from rod-shaped to oval- 

 shaped or elliptical. The nuclear membrane which in the resting 

 nucleus is of very even contour, in the contracted nucleus is often 

 distinctly serrated at the ends, Figs. 28, 29, 88, 89. It often has 

 the appearance of being indented by the contracting fibrillae. 

 Whether this is actually the case is uncertain. 



The contraction node passes along the smooth muscle fiber, caus- 

 ing a distinct enlargement as it goes. As it approaches a nucleus, 

 the nucleus begins to thicken at the end nearest the node, Figs. 20, 

 21, 28, 50, 61, 86. "When the whole nucleus is included in the con- 

 traction node, it assumes its completely contracted, oval form. Figs. 

 19, 21, 23, 29, 89. Occasionally each end of a nucleus may be 

 caught in a c'Ontraction node while the middle lies in an internodal 



