ON ACEPHALA. 395 
brackish waters. According to the observations of Adanson, 
some species can remain six months of the year in salt water, 
and the other six months in fresh. Moreover, it appears 
certain that there are true mussels constantly existing in river 
waters. One species, in fact, belongs to the Danube, and 
another to the lakes of North America. M. Beudant suc- 
ceeded in causing the common mussel to live in water alto- 
gether fresh, by taking suitable precautions. 
Mussels are to be found in all the zones of the earth, 
whether frigid, temperate, or torrid. The identity of our 
mussel with the mus of Aristotle, is allowed by all naturalists 
and commentators. 
The flesh of mussels, which is a sufficiently agreeable 
food, though less so than that of oysters and certain species 
of Venus, very often produces, not only serious, but even 
very alarming symptoms of illness. ‘This would appear to 
take place more in certain places, and at certain times of the 
year than others. The symptoms produced by the hurtful 
qualities of cooked mussels, are said to be an uneasiness, and 
universal numbness which seize the body in about three or 
four hours after the repast. ‘These are followed by a constric- 
tion in the throat, a sensation of heat and swelling in the 
whole head, and especially in the eyes, an inextinguishable 
thirst, nausea, and sometimes vomiting. If the patient has 
not the good fortune to vomit up altogether, or in part, the 
mussels, the constriction of the throat, the swelling of the 
face, of the lips, of the eyes, and of the tongue, increase to 
such a degree as to render speech difficult. The colour of 
these parts becomes so red, that they seem to be excoriated ; 
it extends externally, first to the face, then to the neck, the 
breast, the belly, and in fine, over the whole body. This 
eruption is the most characteristic symptom of the malady. 
It is constantly accompanied with delirium, a singular degree 
of inquietude, an insupportable itching, and sometimes with a 
