POISONOUS MOLLUSCA. 21 



idiosyncrasies of the suiferers. In many cases this latter 

 exphmation will suffice, but sometimes, as in the Leith cases, 

 it is obviously insufficient. Drs. Combe and Christison have 

 reviewed with candour the other supposed causes, and finding 

 reason to refuse assent to any which has been alleged, they 

 agree that the effects seem to be best explained by attribut- 

 ing them to a peculiar poison generated in the fish under 

 unknown circumstances, although the latter eminent physi- 

 cian and chemist admits that in the deleterious mussels he 

 could not detect any principle which did not equally exist in 

 the wholesome ones. It is quite certain that putridity can 

 have no existence as a cause, for the fish are eaten fresh or 

 alive ; and the most delicate chemical tests give no indications 

 of the presence of copper, which, moreover, produces symp- 

 toms of a different character. Delle Chiaie has demonstrated 

 that in many instances the poison is generated with those 

 changes in the system that result from the pregnancy of the 

 Mollusks. The Area noae, Murex brandaris, and M. trun- 

 culus, are great favourites of the Neapolitans, who eat them 

 with perfect safety in all seasons except in summer or the 

 beginning of autumn, when they are dangerous. This author 

 has recorded two examples of their fatal effects at this season ; 

 and another of a party of twelve persons who were poisoned 

 with the Area noae, although the only one of the party who 

 died was the wife of the host. On dissection, he found that 

 all these Mollusca, at this season of fecundity, were greatly 

 altered, more especially the gland that secretes the purple fluid ; 

 and the ovaries, the branchiae, and indeed the whole body 

 were filled with a clammy liquid.* I am inclined to believe, 

 with Dr. Thomas, f that in other cases the poisonous prin- 

 ciple proceeds from some particular food which, not fatal to 

 the Mollusks, yet generates a diseased condition of the body 

 deadly to other creatures. The Leith mussels were living in 

 a dock, where we may presume they were nurtured and fat- 

 tened amid putrescent matters ; and Dr. Coldstream, than 

 whom no one is better qualified to decide the point, gave it 

 as his opinion that the liver was larger, darker, and more 

 brittle than in the wholesome fish, and satisfied Dr. Christison 

 that there was a difference of the kind. The oysters by 

 which, not long ago, some people were poisoned at Havre, 

 were procured from an artificial bed, which had been esta- 

 blished near the exit of the drain of a public necessary : and 

 Dr. Chisholm mentions a fact which bears on the question, 

 and seems to prove that copper communicates some perni- 



* Aiiim. s. Vert. Nap. ii. t Pract. of Physic, G7!). 



