Structure of Smooth Muscle. 535 



nuclei in the fatigued and in the control muscle showed precisely 

 similar, structure. At the same time there was no apparent change 

 in the myofibrillse, the exhausted muscle appearing in no wise dif- 

 ferent from resting muscle in structure. 



5. The effect of drugs on nuclear contraction. 



The effect of a number of drugs on the contraction of smooth 

 muscle nuclei was observed. Among those employed were cocaine, 

 pilocai'pine, apomorphine, adrenalin and atropine. Atropine and 

 cocaine are in certain doses muscle narcotics. In muscle placed in 

 these solutions until the tissue is completely relaxed, the nuclei 

 show the structure of typical resting nuclei. Figs. 90-92 are nuclei 

 from intestinal muscle of N^ecturus, relaxed by placing in a 1 per 

 cent cocaine solution. Pilocarpine was the usual Sitimulant em- 

 ployed. Figs. 93-95, 96-99, are from intestinal muscle of N'ecturus 

 contracted by placing in pilocarpine solution. The changes brought 

 about by contraction with this drug are precisely similar to those 

 caused by the other stimuli used. 



IX. Chemical Changes in Smooth Muscle During 

 Contraction. 

 The deep staining of the entire contraction node as compared 

 with the light staining of the internodal segments would seem to 

 indicate that during contraction there is more change in the muscle 

 fiber than can be attributed to increase in the thickness of myo- 

 fibrillse alone. The difference in staining reaction between the 

 contracted and uncontracted muscle is so striking as to indicate a 

 marked chemical change. With iron-haematoxylin the contraction 

 nodes stain readily and intensely black. Figs. 1, 2, 3, 5, 11, 23. 

 Of course since iron-hsematoxylin is largely a physical stain, this 

 may be due to the condensation of the fiber and swelling of the myo- 

 fibrillse at the contraction node. But the contrast seems entirely 

 too sharp to be due to this alone. With Delafield's hematoxylin 

 and a counterstain of eosin the contraction nodes stain much more 

 intensely with eosin than do the internodal segments. Figs. 20-22. 

 The picric acid in Van Gieson's mixture gives a like effect, Fig. 

 28. Mallory's anilin blue connective-tissue stain is a valuable dif- 



