586 ROBERT MATHESON 



mation of a well defined and somewhat extensive intima which' 

 lines the interior of the oesophagus and so forms an excellent 

 resilient tube down which the food may pass. A basement mem- 

 brane is always present. 



The muscles, as shown in figure 3, present an arrangement well 

 fitted for the work they perform — the transfer of the food from 

 the pharynx to the gizzard. Next the basement membrane are 

 the longitudinal muscles, which are so arranged that the fibers 

 all run obliquely, crossing each other at a rather acute angle and 

 by this means giving them the effect of two oblique cylinders 

 one woven into the other. These fibers in the region of the giz- 

 zard are gathered up into six bundles which pass under the large 

 longitudinal folds (fig. 3) to their points of insertion on the bases 

 of the anterior teeth. Lying directly external to the longitudinal 

 muscles are the circular muscles, small and few, yet with an appar- 

 ently definite arrangement (figs. 3 and 8, cm.). In the region in 

 front of the gizzard the circular muscles increase rapidly in size 

 and number while from the middle of the gizzard to its caudal end 

 they appear as a dense, thick mass. 



From the arrangement of the muscles their action may be read- 

 ily assumed without actual experimental observation on the living 

 animal. On the reception of food the gradual contraction would 

 force it onward and their relaxation, aided by the resiliency of the 

 intima, would distend the lumen for the intake of more food. 

 Thus there would be a somewhat peristaltic action throughout 

 the length of the oesophagus. This peristaltic action has been 

 observed in the living specimen and described in discussing the 

 pharynx. 



The gizzard 



The oesophagus passes into the gizzard without any marked 

 constriction. Viewed externally the gizzard presents a barrel- 

 shaped appearance. The only outward means of locating its 

 beginning is by a slight enlargement and an increase in the thick- 

 ness of the circular muscles. The circular muscles are most 

 greatly increased directly in front of the middle of the gizzard. 

 This increase occurs at the point where the teeth of the gizzard 



