Chapter XVII — 199 — Economic Importance 



content. Further details of this problem are given by Dyer et al. (1944) 

 who have developed what they believe to be a practicable method for 

 determining the index of spoilage by measuring the pU at the surface of 

 fish or fillets with a glass electrode. The range of fresh fish flesh was 

 found to be from pH 6.2 to 6.8. Between pH 6.8 and 7.5 the fish was 

 found to be in an incipient stage of spoilage, and above pK 7.5 the fish 

 is in an advanced stage of decomposition. The test was applied during 

 a two year period to cod, haddock, and flounder with equally satisfactory 

 results. 



Histamine produced post mortem in fish muscle as a result of bacterial 

 activity is believed by Geiger et al. (1944) to be a good criterion of the 

 keeping quality or stage of decomposition of fish. Histamine results from 

 the decarboxylation of histadine, one of the amino acids composing fish 

 flesh. 



Many theories have been advanced to account for the occurrence of 

 poison in mussels and other shellfish. Ptomaine or toxin production by 

 putrefactive microorganisms has been regarded as a possible cause. How- 

 ever, it has now been established by the observations of Sommer and as- 

 sociates at the University of California that the food of shellfish is the 

 source of the poison. The poisonous food has been showTi to be a dino- 

 flagellate called Gonyaulax catenella. Gonyaulax digitate, G. polygrammay 

 G. spinifera, and G. triacontha may be involved also, although most out- 

 breaks of mussel poisoning on the California and Oregon coasts have been 

 associated with an abundance of G. catenella in coastal waters. There is 

 some evidence that species of Ceratium, Prorocentrum, Gymnodinium, 

 Noctiluca, and possibly other genera of diatoms or dinoflagellates may 

 contain the toxic principle. The identical poison has been demonstrated 

 in sand crabs. Further information and additional references on shellfish 

 poison are given by Sommer et al. in Archives of Pathology, Volume 24, 



pages 537-559 (1937)- 



Seaweeds which are used for food, agar, alginates, fibers, insulation, 

 paper pulp, and other purposes are susceptible to decomposition by bac- 

 teria during transportation and storage. Unfortunately little is known 

 regarding the microorganisms responsible for the spoilage of seaweeds. 

 Control measures are largely lacking in scientific principles and effective- 

 ness. 



* * * 



Ambergris is a solid, fatty substance produced by the sperm whale. 

 Pure ambergris has a peculiar sweet, earthy odor which makes it invalu- 

 able as an ingredient of perfumes, but that found floating in the sea and 

 in the intestines of whales has a disagreeable smell. It has been suggested 

 that the activities of bacteria which slowly decompose crude ambergris 

 are responsible for its foul odor. On the other hand, Beauregard (1897) 

 stated that bacteria tend to purify ambergris by decomposing extraneous 

 material. From concretions of ambergris he isolated an organism which 

 he called Spirillum recti physeteris. 



