22 BULLETIN 819, U. S. DEPARTMENT OF AGRICULTUKE. 



The possibilities of contamination in the process of handling just de- 

 scribed may now be considered. Disregarding, for the moment, the 

 fact that the oysters may contain the yeasts when taken from the beds, 

 it may be noted that they are immediately brought in contact with the 

 deck of the boat, which is known to be infected. This, then, is one 

 possibility of contaminating the outside shell of the oyster. Later 

 the oysters are placed in tubs, wheelbarrows, and bins which are also 

 known to be infected, presenting further opportunities for contamina- 

 tion. From the time that the oysters are taken from the water until 

 they are opened in the oyster house there is every chance for the out- 

 side of the oyster shell to become contaminated with the pink yeast, 

 but practically no chance for the contents of the oyster shell to be con- 

 taminated, since the oyster closes its shell and remains tightly closed 

 during the process of handling. On opening the oysters, however, 

 some of the dirt on the outside of the shell is unavoidably transferred 

 to the dipper of opened oysters. Although these oysters are thor- 

 oughly washed, small organisms like the pink yeast are not easily 

 washed off, and may be carried along into the shipping cans. 



The data collected show that the house, the boats, and the utensils 

 within and about the house are heavily infected with the pink yeast, 

 that no yeasts were found in the mud at the bottom of the bay, and 

 that yeasts were present in a very small number of the water samples. 

 While it is true that some oysters when taken from the water contain 

 small numbers of pink yeast, such oysters are not often found, and it 

 is not probable that this is an important source of infection. The re- 

 sults of this investigation indicate that the source of the trouble lies in 

 and about the oyster house. If measures are taken for preventing con- 

 tamination there, the trouble from the pink yeast will be eliminated. 



The fact that the pink yeast is occasionally found in water sam- 

 ples and on oysters taken from the oyster beds may possibly be 

 explained in the following manner. Every season oysters are 

 brought to the oyster house, where they are culled, and then taken 

 back to the oyster beds. Such oysters are contaminated in the 

 process of handling and no doubt carry back the pink yeast with 

 them to the bay. A further explanation, which seems more prob- 

 able, is that the shells that are carried down the bay and planted 

 in the summer may be bearers of the pink yeast. After opening 

 the oysters in the oyster house the shells are clumped in a large pile 

 on the adjacent grounds and left there until June or July, when 

 they are taken to the oyster beds and planted in order to give a 

 smooth, clean surface for the oyster spat and also to furnish cal- 

 cium salts for the growing oyster. These shells are contaminated 

 with the pink yeast after passing through the house, and it is known 

 that the pink yeast grows aboundantly in the shells and in the 



