1887.] 



and its Relation to Putrefaction. 



457 



certain bacteria. In the same way the muscles of certain fish, either 

 because of their peculiar chemical composition, or because of the 

 peculiar disposition and structure of the tissues composing them, lend 

 themselves less readily than the muscles of others to the invasion of 

 the putrefactive organisms. It is well known that at even compara- 

 tively low temperatures fish rapidly putrefy when the atmosphere is 

 loaded with moisture, and that when the atmosphere is dry even at 

 fairly high temperatures putrefaction is comparatively slow, and as- 

 dried gelatine is protected from the attacks of most organisms, by 

 drying fish putrefaction is arrested generally in ratio to the complete- 

 ness of the desiccation. 



It is scarcely necessary to point out the practical bearing of this 

 inquiry. 



In fish putrefaction, when it once sets in, proceeds much more 

 rapidly than in other vertebrates. This being the case, fish should 

 be used as soon as possible after the rigor disappears. Inspectors 

 of fish markets and fish dealers have various empirical tests by which 

 they believe they are able to determine whether fish are or are not fib 

 for food. They especially trust to the colour of the gills, the firmness 

 and colour of the muscles, and the nature of the odour. As a matter 

 of fact, it is often almost impossible to say whether a fish is or is not 

 fresh after the rigor has disappeared. There is often a pause in the 

 putrefactive process (caused probably by the first crop of bacteria 

 being destroyed by their own bye-products). For this reason it is 

 desirable fish should be used as soon as possible after the rigor has 

 vanished, and that fish, intended for preservation (it matters little 

 how), should be treated, if possible, while the rigor lasts. 



I have made numerous experiments with ice for preserving fish. 

 It is generally alleged that fish which have been preserved for some 

 time in a frozen state have lost much of their flavour. This I find 

 depends partly on when the freezing is effected and partly on the 

 temperature maintained. Fish which are frozen after the rigor has 

 gone have either very little flavour or they are tainted with offensive 

 septic products. But fish which have been frozen before rigor sets in 

 (which have probably never stiffened) are equally without flavour, and 

 they rapidly soften and disintegrate when raised to ordinary tempera- 

 tures. On the other hand, fish which are frozen immediately after 

 the rigor sets in remain almost unaltered, and when cooked can 

 scarcely be distinguished from fresh fish unless the temperature has 

 been unnecessarily low. The most perfect results were obtained by 

 keeping fish (both salt and fresh water) at a temperature varying 

 from —1° to — 2° C. Haddocks which were pithed and gutted and 

 preserved in water-tight insulated chambers at a temperature of — 2° C. 

 for three weeks continued rigid from first to last, and when cooked 

 were firmer and better flavoured than ungutted fish only ten hours out 



