no. 9 musculature of the blue crab cochran 6l 



Ossicles of the Stomach 



In order to give the necessary rigidity to the stomach in the break- 

 ing up of food particles to aid in their rapid assimilation, the stomach 

 is equipped with a complicated mechanism composing the so-called 

 " gastric mill." A series of strategically placed ossicles gives places 

 of attachment externally to the muscles, and inside the stomach most 

 of the ossicles are tooth-bearing so that they may effectively pulverize 

 the food before it passes on to the next stage of digestion. These 

 ossicles may be considered under separate headings according to their 

 function and position. 



OSSICLES OF THE " GASTRIC MILL " 



/. Mesocardiac ossicle. Single. — This small median ossicle lies in 

 the dorsal wall of the cardiac region of the stomach and is almost 

 completely fused with the urocardiac ossicle, which lies behind it. In 

 front it is bounded on either side by the pterocardiac ossicles. It gives 

 a firm attachment to the anterior ends of the cardiopyloric muscles, 

 since it is especially thickened at this point. (Figs. 25 A, 27, 28.) 



//. Pterocardiac ossicles. One pair. — These ossicles lie on either 

 side of the foregoing and meet each other in front of it, projecting on 

 either side with their wing-shaped outer ends nearly at right angles to 

 the midline of the stomach. One of the pair of anterior gastric muscles 

 (ip/) is inserted on the widened inner border of each ossicle. The 

 attenuate tip of the ossicle approaches the outer border of the zygo- 

 cardiac ossicle, with which it is closely connected. (Figs. 25 A, 27, 28.) 



///. Zygocardiac ossicles. One pair. — This pair of ossicles lies in 

 the superolateral wall of the cardiac region of the stomach and is the 

 largest and strongest of the ossicles. Externally, they appear as 

 slender curved structures, the anterior end in close connection with 

 the tips of the pterocardiac ossicles, and their posterior end with the 

 exopyloric ossicles. When the stomach is opened, the zygocardiac 

 ossicles are found to project inward, thickening greatly and bearing on 

 their inner opposed surfaces the " lateral teeth," consisting of one very 

 heavy denticle of tough chitinous material followed by two smaller 

 single ones and by a double row composed altogether of about 20 very 

 pointed small denticles, directed inward and growing smaller in size 

 posteriorly, the area between them without ridges. (Figs. 25 A, B, 

 26, 27.) 



IV. Exopyloric ossicles. One pair. — These ossicles appear exter- 

 nally as short and nearly straight structures lying diagonally near the 

 lateral posterior border of the stomach. The outer end of each ossicle 



