ON THE STOMACH IN MAN AND THE ANTHROPOID APE. 21 



process is in progress. At the same time it should be borne in mind that, even granting 

 that this takes place in the cat, it does not necessarily follow that a similar event occurs in 

 the primate. The pyloric canal of the cat, in so far as its musculature is concerned, is 

 not so distinctly specialised, nor is this section of the stomach so obviously a separate 

 part of the organ as in man and the anthropoid ape. 



The pyloric region of the cat in several specimens has been examined, and sections were prepared for 

 microscopic study in the same manner as in the case of the human stomach (PI. II. fig. 20). 



The pyloric canal of the cat is relatively longer than in the primate ; but although it forms an obviously 

 distinct part of the stomach, its demarcation from the pyloric vestibule is not so definite, seeing that, in both 

 the full and empty states of the organ, the entire length of the pyloric portion is more or less tubular, and 

 the pyloric vestibule does not present the appearance which is characteristic of man and the anthropoid. 



The duodeno-pyloric constriction is very pronounced on the greater curvature side, where it forms a deep 

 indentation. On the opposite aspect there is little indication on the surface where the stomach ends and 

 the intestine begins. 



The musculature of the pyloric canal also differs in some particulars from that in man. It is more 

 massively developed on that aspect of the canal which corresponds to the greater curvature than on the 

 opposite aspect. On this side likewise the sphincteric ring attains a great thickness, and stands out very 

 prominently. On the lesser curvature side a special thickening of the circular musculature at the duodeno- 

 pyloric junction does not exist even in the contracted state of the muscle; at least, in none of the specimens 

 which I have specially prepared does such a thickening exist in this situation. On the lesser curvature side, 

 therefore, except when the musculature of the pyloric canal is contracted (as in fig. 20), the circular coat is 

 not sharply marked off from that of the intestine or of the pyloric vestibule. 



Again, the longitudinal fibres of the pyloric canal do not present the same intimate relation to the 

 sphincteric ring as in man. On the lesser curvature side they are very poorly developed and do not enter the 

 circular coat ; and even on the opposite side, where the ring is strongly pronounced, I have not been able to 

 trace any of them into it. 



Upon the whole, I am inclined to believe that the sphincteric cylinder in its whole 

 length exercises a double function, and acts both as a retaining and as an expelling agent. 

 Hirsch (20), in a short but very important paper, gives a graphic account of the force 

 with which material is ejected from the stomach into the duodenum ; * and Cannon (6) 

 describes the manner in which he saw it ' spurted ' from the one into the other. The 

 high pressure which is employed in propelling a portion of the gastric contents into the 

 intestine can be easily understood when we remark the power of the musculature which 

 surrounds the wall of the pyloric canal. But, having made this effort, there is some 

 reason for the belief (until more conclusive evidence on the other side is forthcoming) 

 that during digestion the sphincteric muscular cylinder in its whole length remains 

 contracted until the time for the expulsion of another portion of the gastric contents 

 comes round. 



While engaged in the consideration of the various problems suggested by the 

 structure of this part of the stomach, my colleague, Mr Harold Stiles, directed my 

 attention to the important lesson which may be learned regarding the function of the 

 pyloric canal from cases of so-called pyloric stenosis in infants ; and through his generous 



* Hirsch describes it thus : " Die Intervalle waren in den ersten Stunden kiirzer und die ausstromenden Massen 

 verliessen die Kanule imter starkerem Druck (im Bogen), in den spateren Stunden wurden die Intervalle etwas liinger 

 und das Ausstromen fand unter Schwacherem Druck statt." 



