538 V. S. BUREAU OF FISHERIES 



(b) Bacteriological examinations. — A large number of fish-agar Petri dishes 

 were inoculated with samples of muscle from gutted and ungutted herrings 

 after four or five days at ordinary temperature, and comparisons were made of 

 the amount of bacterial growth produced. The result was that in about two- 

 thirds of the total number of plates the largest amount of growth came from 

 gutted herrings. In view of the fact that the bacteriological samples were 

 taken with extreme care in every case, and the muscle always taken from the 

 same part of the fish, it was proved pretty definitely that more bacteria made 

 their way into the muscle tissues of the gutted than of the ungutted specimens. 



This result is due to the gutting process, wherein a large amount of gut 

 contents are left behind upon the inner body wall ; and although much of it is 

 washed off in the brine tank, a large number of gut bacteria penetrate the flesh 

 and start putrefaction more quickly than in the case of the ungutted fish, where 

 the bacteria are imprisoned within the gut whose wall has first to be pene- 

 trated. Moreover, in the case of the gutted fish the inner as well as the outer 

 surface is exposed to foreign contamination of all sorts, particularly after com- 

 ing out of store, and this certainly hastens putrefaction more than when only 

 the outer surface of the fish is open to infection. 



It ought perhaps to be mentioned that the colonies produced on all the plates 

 were chiefly of the same kind, namely, moist, round, buff-colored, fairly large, 

 irregular-sized, Gram negative diplococci. All the plates gave off a strong 

 smell of ammonia after the third day. 



The strong smell of the fish referred to evidently was oxidation 

 or rusting of the fat. The fish were kept at from 18 to 25°, which, 

 of course, is far too warm to prevent rusting. These excessively 

 warm temperatures may explain in large measure the difference she 

 found. 



This criticism applies to much of the otherwise valuable research 

 work done in England and in Europe on freezing and cold storage 

 of fish. The work of Plank, Ehrenbaum, Reiiter, Stiles, Fortuyn, 

 and others applies largely to freezing and storage at temperatures 

 much above zero. It is well known in this country that satisfactory 

 results can not be so produced. 



WASHING 



The commonest method of washing is to dump the fish, together 

 with the ice in which they are packed, into a trough of water. This 

 trough usually has a slat framework in the bottom and a standpipe 

 for overflow of water. Usually water runs continuously into and 

 out of the tank. Water serves to wash the fish and at the same 

 time to remove the cracked ice. Sometimes the fish are roused about 

 in the water with a wooden rake. When the washing consists in 

 no more than putting a large quantity of fish into a small quantity 

 of water and taking them out to pack them obviously it can do little 

 good. The slime is tenacious and is the breeding ground of bacteria. 

 Blood and pieces of gut are on and in the fish. The water quickly 

 becomes a heavy culture of bacteria, which would do much more 

 harm than good to a really fresh fish. Green (above referred to) 

 says " finally, if fish, when gutted, can not be washed in running 

 water they are far best left unwashed altogether." 



Where a large volume of water is running vigorously and freely 

 over and among the fish it does more good, especially in ungutted 

 fish. There is also the question of washing off slime, which is not 

 always desirable. A fresh eel, for example, if frozen with the slime 

 on will look more natural after defrosting than it would if it had 

 been washed thoroughly. It is the view of some, also, that the slime 



