SEA-FISHEBIES LABORATORY. 85 



few investigators, viz., that some — by no means all — of 

 our oysters and mussels are grown or kept under most 

 insanitary conditions, and may when taken as food, 

 without the necessary precautions, from unhealthy local- 

 ities, cause disease or poisoning. Since the publication 

 of this "Yellow book" there has been a certain amount 

 of complaint, and even some indignant remonstrance 

 from oyster producers, much inquiry on the part of the 

 public, and some correspondence in scientific journals. 

 It seems to me that a few points want to be clearly stated, 

 and some conclusions drawn as to the future regulation 

 of our shellfish trade. 



In the first place, out of the various forms of human 

 poisoning which can be caused by food, shellfish, under 

 unhealthy conditions, may give rise to two which are very 

 distinct from one another. They are : — 1. Bacterial 

 infection, due to the presence of actual living disease 

 germs, derived presumably from sewage. 2. Intoxication 

 with organic poisons developed in the body of the oyster 

 or mussel. 



We need scarcely consider the third possible case, 

 poisoning by means of copper salts taken into the body of 

 the shellfish from its environment, as this, if it ever 

 occurs, must be very rare. All oysters contain a little 

 copper in their blood, but not enough to do any harm. 



We are left then with the two possible causes of disease 

 — specific bacterial infection and organic poisons. If a 

 case of typhoid arises from eating an oyster, then we 

 suppose that oyster must have contained the living 

 typhoid bacilli, and these must have reached the oyster 

 from some previous case of typhoid — that is bacterial 

 infection, and the disease only develops after the proper 

 and considerable interval. If, on the other hand, more or 

 less severe gastric derangement and other symptoms of 



