REPORT OF COMMISSIONERS OF INLAND FISHERIES. 157 



have been overlooked by everyone except Albert and is, in our 

 opinion, of great importance (see page 158). The cardio-pyloric 

 muscle, a small band, extends from the upper end of the anterior 

 dorso-lateral pyloric plate and the adjacent upper edge of the lateral 

 tooth f oi'ward above the outer end of the cardiac ossicle to the upper 

 part of the anterior edge of the ptero-cardiac ossicle. 



The plates, teeth, and muscles described above form the essential 

 parts of the gastric mill, which consists of two portions, the median 

 and the lateral, which are so closely connected that their actions are 

 absolutely coordinated. 



The median portion of the gastric mill includes the four median 

 plates mentioned above and the anterior and posterior gastric 

 muscles. The two horizontal plates, the cardiac and pyloric, are 

 connected by the urocardiac plate and the median tooth, the former 

 being attached to the latter at the junction of its lower and middle 

 thirds. The contraction of the anterior and posterior gastric muscles 

 draws apart the cardiac and pyloric plates and as these plates sepa- 

 rate the urocardiac ossicle pulls the lower end of the median tooth 

 forward, the former acting as the power applied to the latter as a 

 lever of the third order at a point about two-thirds of the length of 

 the lever from the fulcrum, i. e., the articulation of the median tooth 

 with the pyloric plate. Thus the median tooth is drawn forward 

 with great force. 



The lateral portion of the gastric mill consists of: 



The pterocardiac bar which is hinged on the outer end of the cardiac 

 plate so as to make a right angle with that plate and so that its lower 

 end moves from the position of rest inward and backward in a ver- 

 tical plane inclined forward at an angle of 75 or 80 degrees with the 

 sagittal axis; the lateral tooth whose anterior upper angle is attached 

 to the pterocardiac bar and so moves inward and backward with that 

 point and whose posterior'upper angle is fixed to the outer anterior 

 angle of the pyloric plate; and the anterior dorso-lateral pyloric 

 plate which receives the insertion of the postero-lateral gastric muscle 

 and which is attached to the posterior edge of the lateral tooth. The 



