of a fresh wet sample and between 42 and 57 

 percent of a dry sample. The figures quoted 

 above from the paper by Wentworth and Lewis 

 (1958) refer to the oysters of Apalachicola Bay, 

 Fla., the extent of fluctuations is probably common 

 to all oysters of the Atlantic and Gulf states since 

 occasional observations on oysters from various 

 states fall within this range (Jones, 1926). Ac- 

 cording to monthly observations by Gaarder and 

 Alvsaker (1941), the protein content in the meat 

 of 0. edulis from Norwegian ponds ranks somewhat 

 higher, varying from 8.8 to 11.2 percent (fresh, 

 wet basis) with an annual average of 10.5 percent. 



Interesting biological observations were made 

 by Duchateau, Sarlet, Camien, and Florkin (1952) 

 on free amino acids in the muscles of marine bi- 

 valves, 0. edulis and Mytilus edulis, and the fresh- 

 water mussel, Anodonta cygnea. The muscles of 

 these mollusks were isolated after bleeding, boiled 

 for 5 minutes to inactivate proteolytic enzymes, 

 homogenized, and treated wdth tungstic acid. 

 Protein-free samples were hydrolyzed and ana- 

 lyzed. The results (table 43) show that the 

 amino acid contents differ greatly between the 

 marine and fresh-water species. Generally higher 

 concentrations of amino acids in the muscles of 

 marine forms is related to the osmotic equilibrium 

 with the blood, which in these anunals has nearly the 

 same concentration as that of sea water. Because 

 the concentration of inorganic ions in the tissues 

 is lower than in the blood, a relatively high con- 

 centration of free amino acids in the tissues is 

 necessary for maintaining osmotic equilibrium. 



The concentration of protein in blood plasma 

 in 0. edidis, Pecten maximus, j\Iya arenaria, and 

 Mytilus edulis is about 0.1 percent (Florkin and 

 Blum, 1934). Samples of blood were collected 



T.ABLE 43. — Free amino acids {mg./lOO g. of ivater) in the 

 muscles of marine and fresh-water bivalves* 



Alanine.-- 



Arginine 



Aspartic acid-. 

 Glutamic acid. 



Glycine 



Histidine 



Isoleuciue 



Leucine 



Lysine 



Methionine 



Phenylalanine 



Proline 



Threonine 



Tyrosine 



Valine 



Ostrea 

 edulis 



646.0 

 66.6 

 26. 1 



264.0 



248.0 

 22.9 

 19.2 

 12.9 

 22.0 

 8.4 

 8.5 



166 

 9.7 

 10.3 

 10.8 



Mytilus 

 edalis 



340 



415.5 



200.4 



317.0 



399.0 



12.1 



24.8 



15.4 



39.4 



9.8 



9.6 



29.0 



30.5 



12.7 



14.4 



Anodonta 

 cygnea 



8.8 

 36 5 

 4.4 

 29.4 

 13.2 

 2.5 

 6.3 

 3.6 

 8.2 

 0.4 

 1.6 

 1.0 

 3.6 

 2.2 

 3.3 



after tearing off the gills, and the cells were 

 removed by centrifugation. 



Nutritional studies have been made by feeding 

 )'aw and frozen oysters to albino rats suffering 

 from artificially induced vitamin deficiency (Ran- 

 doin and Portier, 1923; Jones, Murphy, and 

 Nelson, 1928; Whipple, 1935). E.xperimental 

 results showed that oysters are a good source 

 of vitamins A, B, and D. Daily feeding of 2 g. 

 of fresh Chesapeake Bay oysters (0.32 g. on a dry 

 basis) furnished sufficient vitamin A to cure rats 

 of xerophthalmia (chronic inflammation and 

 thickening of the conjunctiva of the eye) in 18 to 

 20 days. According to Whipple's data the 

 vitamin content of oysters taken in October from 

 Great South Bay, Long Island, N.Y., was ap- 

 proximately three LT.S.P. units/g. The vitamin 

 D content of oysters harvested from the same 

 bay in the faU was approximately 0.05 U.S. P. 

 units/g. and the vitamin B (B') content was 

 found by Whipple to be approximately 1.5 

 Sherman units/g. Oysters are a very modest 

 source of vitamin D and their antiricketic value 

 is low. 



In more recent work Wentworth and Lewis 

 (1958) determined by chemical analyses the 

 contents of niacin, riboflavin, and thiamine 

 (table 44). None of these vitamins was found to 

 have a distinct pattern of seasonal fluctuation. 



Table 44. — Range of vitamin contents in Apalachicola, 



Fla., oysters in mg./lOO g. wet weight 

 [From February 1955 to August 1956 From Wentworth and Lewis, 1958] 



•From: Duchateau, Sarlet. Camien, and Florkin, 1952. The French 

 investigators express the concentration in a rather iinique manner as mg./ 

 100 g. of "d'cau de fibre." 



Thiamine content of raw shucked oysters 

 studied by Goldbeck (194/) varied by region. 

 Oysters collected in the waters of Connecticut 

 and New York contained more thiamine per unit 

 of fresh weight than those from Louisiana, Georgia, 

 Virginia, and Maryland (table 45). The determi- 

 nation of thiamine was made by chemical method 

 (using thiochrome) and by rat growth method, 

 which gave values about 9 percent smaller than 

 the chemical tests. 



The sterol mixtures of bivalves are of particular 

 interest, because in certain species they are the rich- 

 est natural sources of provitamin D. In Modiolus 

 demissus of the Atlantic coast of America the 

 content of provitamin D was found to be suffi- 



CHEMICAL COMPOSITION 



391 



