of the Fishery Board for Scotland. 37 



oas in degree, as it is dejecta from a human source ; and finally, the very- 

 great influence which the consideration of such matters is destined to 

 exercise on many public health questions — e.g., Is the presence of bacillus 

 coli synonymous with sewage pollution 1 — I shall not discuss here, as it is 

 not within the scope of this paper. But I may add, in conclusion, that, 

 since for the present the bacillus coli is accepted as the best indicator of 

 excremental pollution, while at the same time bacteriology fails to 

 distinguish between coli bacillus from human sources and those derived 

 from the lower animals, and since from the public health point of view 

 the one or the other has quite a different significance, the bacteriologist 

 in future, having due regard to all local conditions, will require to inter- 

 pret his results more in a relative and less in an absolute sense. For it 

 is only by a judicious weighing of the bacteriological resiilts with all the 

 topographical data that an approximately reasonable and correct estimate 

 can be formed of the potential danger to health regarding many of the 

 important questions which have so frequently been considered by public 

 health authorities. 



18. Summary regarding Detection of Decomposition in Fish. 



After discussing the various factors concerned in the decomposition of 

 fish and the various criteria ordinarily applied in its detection, the 

 important question still remains — how far these criteria are applicable 

 and reliable in the hands of those whose daily duties are the examination 

 of fish. Although it may be conceded at once that it is probably unsafe 

 to consider any one of these criteria as individually absolutely reliable, 

 yet, in reviewing the whole question, I am inclined to consider the 

 following five tests as fairly reliable in giving comparatively trustworthy 

 evidence as regards the condition of a fish : — 



1. The presence or absence of rigor mortis. 



2. The presence, degree of development of. or absence of, reddish 



discoloration on the ventral aspect of the backbone. 



3. The smell. 



4. The manner in which the flesh separates from the backbone. 



5. The appearance of the abdominal walls. 



I. So long as a fish is in the condition of rigor mortis it is a guarantee 

 that it is perfectly fresh, since decomposition can only set in as rigor 

 passes off; the ordinary tests for which, already enumerated, are — degree 

 of rigidity on handling and balancing, flesh firm and elastic and does not 

 pit readily on pressure. The chemical changes in the muscle are also 

 important — acid during rigor, becoming alkaline as rigor passes off, and 

 finally distinctly alkaline when decomposition has set in — both to litmus 

 paper. But since, under the most favourable conditions under which fish 

 are treated, rigor mortis is of short duration, its absence is no guarantee 

 that fish are not sufficiently fresh and not fit for human food. 



II. At this stage the presence or absence of reddish discoloration on 

 the ventral aspect is invaluable, and should always be looked for. If it 

 is present, we know that the fish are certainly quite fresh. The time will 

 probably be about 48 to 60 hours after capture or after landing. But 

 even at this stage the fish may not be such as should be condemned as 

 unfit for human food or for curing purposes. Yet, when one sees this dis- 

 coloration fully developed, it should make one suspicious and more 

 cautious as regards the condition and cause one to examine them more 



