The Histogenesis of Smooth Muscle in the Alimentary- 

 Canal and Respiratory Tract of the Pig. 



By 



Caroline McGill, A. B., A. M. 



Instructor in Anatomy, University of Missouri. 



(With Plates VII— XI. 1 Fig.) 



Contents. 



I. Introduction. 

 II. Review of the Literature. 



III. Material and Methods. 



IV. Histogenesis of Smooth Muscle. 



1. Early Development. 



2. Formation of the Muscle Layers 

 in the Alimentary canal. 



•S. Rate and Character of Growth of 



Smooth Muscle. 

 4. Formation of Myofibrillae. 



5. Development of the Interstitial 

 Connective Tissue. 



6. Development of the Smooth 

 Muscle in the Respiratory Tract. 



7. Comparison with Adult Smooth 

 Muscle. 



V. Summary. 

 VI. Literature List. 

 VII. Explanation of Plates. 



I. Introduction. 



The purpose of this paper is to give a detailed account of the 

 histogenesis of smooth muscle as it is found to occur in one of the 

 higher vertebrates. In addition, the histology of adult smooth muscle 

 is considered with special reference to the structure from the stand- 

 point of its histogenesis. The complete development of smooth muscle 

 has not, as yet, been traced in any vertebrate. The few investigators 

 who have worked upon this subject have confined themselves to the 

 early stages of development, no one having followed the histogenesis 

 through, even in a general way, to the adult muscle. Of those who 

 have written upon the early development, practically all have attempted 

 to determine merely from which germ layer the tissue is derived, and 



International!- Monatsschrift f. Anat. u. Phys. XXIV. 14 



