Figure 67. — Apparatus used for determining the elastic force of the ligament. A — oy.ster shell; B — support; C — mercury 

 manometer mounted on wall; D — air pump; E — two dry cells to operate the signal magnet M ; F — plunger of hypo- 

 dermic syringe resting on right valve above muscle attachment area; G — stand upon which the syringe is mounted; 

 K — kymograph; L — three-way stopcock; M — signal magnet with writing pen; N — lever connected to upper valve of 

 the oyster A; S — key switch for signal magnet. 



18.45g. Both syringe and piston were cleaned and 

 lubricated at the beginning of each series of ob- 

 servations and the weight of the piston in the 

 operating position checked frequently. Prior 

 and during the determination, which required 

 only a few minutes, the ligament was kept moist 

 by frequent applications of a few drops of sea 

 water. 



To convert the manometer readings into force 

 in grams, the following simple computation was 

 made: since the cross-section area of the piston 

 in the syringe is 1.971 cm.^ and the specific gravity 

 of mercury is 13.95, the weight of the column of 

 mercury is equal to 1.971 x 13.95 x H wliere H 

 is the height f)f that column in centimeters. 

 Determinations of elastic force made by this 

 method are accurate within 5.3g. since readings 

 were taken at 2 mm. intervals and the weight 

 of a mercury cokunn of 1 cm. height is 26.71g. 



With exposure to air the elasticity of the liga- 

 ment changes, gradually losing its resilience. As 



THE LIGAMENT 



733-851 O— 64 5 



drying progresses greater force must be applied 

 to bring the valves together, and the ligament 

 becomes harder and more brittle until it finally 

 breaks along the pivotal axis. The rate of these 

 changes was ascertained in two tests with large 

 xVmerican oysters from Peconic Bay, N.Y. After 

 the shell was placed in the apparatus (fig. 67) 

 determinations were made at 15-minute intervals 

 between which the ligament was not moistened. 

 Room temperature varied slightly from 68° to 

 70° F., and relative humidity in the laboratory 

 was 46 percent. The results of testing which 

 continued for 5 hours and 5 minutes indicate that 

 under the conditions of the experiment no signifi- 

 cant change in the physical properties of the 

 ligament is noticeable during tiie first 90 minutes. 

 After that the hardness of the ligament increases 

 steadily as can be seen from the shape of the curve 

 in figure 69. The test repeated a second time 

 yielded similar results. It can, therefore, be 

 deduced that under the given experimental condi- 



61 



