MAINE SARDINE INDUSTRY. 81 



exists in the skin or flesh of the fish. Different combinations of sul- 

 phur, in the form of cystein, cystin, and keratin, are found in animal 

 tissues. The first two occur in the true proteins or meat tissues, 

 while the last is the principal sulphur-bearing constituent of hair, 

 nails, skin, etc. Theoretically, if sulphur has any relation to detin- 

 ning, that in skin should exert the least effect. To a certain extent 

 this is confirmed by the results of the experiments. 



The examination of a few cans from these packs three months 

 after they had been processed showed that portions of the surface 

 of the cans containing the unskinned fish had become blackened or 

 detinned, usually where the skin of the fish came in contact with the 

 can. In rolling the lid back or in taking the fish from the can pieces 

 of skin adhered to the lid or bottom of the can. The surface imme- 

 diately below this was detinned and sometimes slightly pitted, while 

 the surface of the can not in contact with the fish remained bright. 

 The interior surface of the cans containing the skinned fish showed 

 black markings on both the lid and bottom, in some instances a little 

 more marked than in the cans of the unskinned pack. In the pack 

 of skinned fish the entire surface of the can, although not black, was 

 tarnished or dulled. The detinning appeared to be more general 

 over the whole surface, that is, there were no bright places on the 

 surface, as was the case in the pack of unskinned fish. It was quite 

 evident that more corrosion of the surface of the can occurred in the 

 pack of skinned fish than in the pack of the unskinned fish. 



After standing six months, the same markings in the interior of the 

 cans, perhaps a little more pronounced, were found in the cans of 

 unskinned fish. Several places where the fish had come in contact 

 with the surface of the cans were detinned and slightly pitted. The 

 portions of the cans not touched by the fish remained bright and 

 untarnished. All the cans examined were attacked to about the 

 same extent. The skin that adhered to the cans was carefully 

 removed and added to the sample for analysis. Besides being tar- 

 nished, the surface of the cans containing the skinned fish was badly 

 pitted, and small pieces of the fish adhered to the cans at the end of 

 six months. This pitting and adherence of the flesh to the surface 

 of the can had not taken place after three months' standing. 



After six months' standing the interior surface of the cans con- 

 taining the skinned fish had been attacked to a greater extent than 

 had the surface of those in which the unskinned fish were packed. 

 In both cases more corrosion was shown after six months' standing 

 than after three months' standing, and in both instances it was more 

 marked in the case of the unskinned fish. 



The water, oil, and tin contents of samples of these two packs are 

 shown in Table 35. 



5890°— 20— Bull. 908 6 



