SPECIFIC GRAVITY OF BLOOD 



The osmotic pressure of body fluids of bivalves 

 is about equal to that of the surrounding water 

 so it may be expected that the specific gravity 

 of blood approximates tliat of the water. For 

 determining the specific gravity of blood or of 

 pericardial fluid, the falling drop method of 

 Barbour and Hamilton (1926) has been used. 

 The procedure consists of timing a drop of fluid 

 of uniform size as it falls a distance of ,30 cm. 

 thi-ough a mixture of xylene and bromobenzene 

 in a vertical glass tube of exactly 7.5 mm. in 

 diameter. The time is recorded with a stopwatch 

 accurate to one-tenth of a second. The speed of 

 falling of a drop of the sample is compared with 

 that of a drop of the same size of standard potas- 

 sium sulfate (K2SO4) solution of known density. 

 By using an alignment chart (supplied with the 

 instrument), correction is made for room tem- 

 perature; the specific gravity of the sample can 

 be calculated with an accuracy of 1 times 10~*. 

 The source of error caused by variations in the 

 size of drops is minimized by using an automatic 

 Guthrie pipette controller. The method is simple, 

 rapid, and gives consistent results. In tliis way 

 the specific gravity of blood was determined foV 

 oysters taken from various environments. 



A series 01 tests was also made to record changes 

 that occurred in oysters placed in diluted sea water 

 and in those exposed to air. The blood collected 

 from the ventricle with a glass pipette was centri- 

 fuged for 20 minutes at 1,200 r.p.m. to separate 

 blood cells from plasma. For brief storage the 

 sample of plasma was kept in a paraffin coated 

 container from which portions were taken for 

 determination. Observations were made at the 

 time of full sexual maturity of the oysters in the 

 middle of July and were repeated 2 weeks later 

 at the completion of spawning. All tests were 

 made at 22° C. and salmity 31.0-31.5 7oo. The 

 oysters were collected from Wellfleet Harbor, 

 Mass., but remained in the laboratory tanks for 

 about 3 weeks before the tests. The specific 

 gravity of blood during the July 15 to 18 period 

 varied from 1.0252 to 1.0262; in the tests made 

 after spawning between July 28 and 31 the specific 

 gravity of blood varied from 1.0258 to 1.0259. 

 The results are close to those reported by Yazaki 

 (1929) for 0. circumpicUi in which the specific 

 gravity of blood in the summer specimens varied 

 between 1 .025 and 1 .029. 



CIRCULATORY SYSTEM AND BLOOD 



No significant changes were found in the blood 

 of oysters kept for 72 hours in the refrigerator at 

 temperatures varying from 4.5° to 7.5° C. At 

 the end of the test the specific gravity of the blood 

 of the refrigerated mollusks was 1.0258; and in the 

 controls which were kept in running sea water at 

 21° to 22° C. the blood was 1.0259. 



A gradual decrease in specific gravity occurred 

 in the oysters kept in running sea water of 

 diminishing salmity. The results of this experi- 

 ment are shown in table 31. 



In highly diluted water shell movements of 

 some of the oysters were abnormal and most of 

 the time they remained closed. In these oysters 

 the specific gravity of the blood after 72 hours of 

 exposure to salinity of 9 to 12 °U^ was relatively 

 high (1.0138 and 1.0178) compared to the specific 

 gravity of 1.0092 in the oysters which stayed open 

 for more than 50 percent of the total tune. It 

 may be deduced from these e.\-periments that the 

 oysters kept in water m which the salinity was 

 reduced from 31-32 %„ to 16.7-17.7 °U^ at- 

 tained the osmotic equilibrium of blood in about 

 120 hours. 



Table 31.— Z)ecrease in the specific gravity of cell-free blood 

 of the oyster, C. virginica, in water of lowered salinity 



'Observations discontinued after 72 hours. 



SEROLOGY 



Serological reactions between several moUusks 

 were studied by Makmo (1934), who experimented 

 with the following species; bivalves — Meretrix 

 meretrix, Paphia philipinarum, Ostrea (Cras- 

 sostrea) gigas, Area injiata; g&stro pods— Turbo 

 cernutum, Haliofis gigantea, Rapana thomasiana; 

 cephalopods — Sepiella japonica and Pohjpus 

 variabilis. In these tests the extracts of tissues 

 m physiological saline solution were injected 

 intraperitoneally or subcutaneously into rabbits 

 to obtain the antisera. Injections were repeated 

 for 7 days using doses which increased from 0.5 to 

 5 grams. One ml. of extract and 0.1 ml. of anti- 

 serum were used in performing precipitation tests, 

 and the tube was set aside for 1 hour at 37° C. 

 Positive reaction was obtained with all the species. 

 Ostrea antiserum reacted very strongly with 

 Meretrix and Paphia and less strongly with 



265 



