Proceedings of the Association of American Anatomists 515 



THE SPHINCTER SUPEEIOR. By Eobeet C. Bourlaxd. 



There is on the inner surface of every rectum a transverse fold ex- 

 tremely variable in size and generally situated upon the posterior and 

 right lateral wall about six centimeters above the anus. This structure 

 is the principal valve described by Houston. While the single fold is 

 the condition by far most frequently met with, there may be another 

 fold from one to four centimeters above the first on the opposite side 

 of the gut. When this condition exists, the two folds are generally 

 united, forming one spiral fold completely enclosing the intestine. 

 Other transverse folds above and below are sometimes, though rarely, 

 met with. 



This constantly occurrhig valve consists of a fold of mucous mem- 

 brane enclosing muscularis mucosae, submucosa, and as a rule a thick- 

 ened portion of the circular muscular coat. The circular muscular 

 coat always presents a very distinct thickening, generally situated within 

 the valve and forming the greater part o'f the tissue constituting the 

 base of the valve; occasionally this- thickening is found in the imme- 

 diate vicinity of the valve. 



The most important structural elements of the valve are therefore 

 the fold of the mucous membrane and the above mentioned thickened 

 muscular coat and these need to be considered in determining the sig- 

 nificance of this fold. 



By reason of the fact that an increase of the circular muscular coat 

 is always associated with this valve, partly surrounding the intestine 

 and sometimes, in conjunction with another fold, completely surround- 

 ing it. I feel warranted in the conclusion that the muscle is of primary 

 importance and that the principal valve of Houston represents imper- 

 fectly a third or superior sphincter. 



THE DUCTS OF THE HUMAN SUBMAXILLARY GLAND. By Joseph 

 INIarshall Flint. Anwric<m Journal of Anatomy, VoL I. 



THE PANCREATIC DUCTS IN THE DOG. By Daxiel G. Revell. American 

 Journal of Anatomy, Vol. I. 



VARIATIONS IN THE DISTRIBUTION OF THE BILE DUCTS OF THE 

 CAT. By RoswELL Hill, Johnson. 



This paper is a preliminary account of 85 out of a proposed 100 

 cases. Since a complete analysis will shortly be published only a few 

 of the principal determinations will be given here. 



In 7 cases there was one hepatic duct as in man. In a plurality of 



