ON GASTEROPODA. 341 
and placing it in the form of a sort of cataplasm on the 
cushion of the bandage used in such cases. In a few months, 
he says, two or three hundred of these animals thus applied 
will work acomplete cure. It appears much more likely that 
the cure, if effected at all, is effected by mechanical means. 
It is not necessary to detain our readers by enumerating all 
the properties which have been attributed to these animals, 
which for the most part have been conceived @ priori, from 
the viscosity of the blood, and the calcareous matter which 
their humours contain. Those who are curious on this sub- 
ject may find enough to gratify them in Gesner, and the older 
writers on the medical science. | 
We must, however, dwell a little more on the employment 
which physiologists have made of these animals, and which 
we have already glanced at in our notice of the slugs, to 
prove that reproduction is not confined to less essential parts, 
and to animals but little raised in the scale of being, but that 
it may equally take place as to the composition of numerous 
and very important organs, and even in the head itself. 
Spallanzani positively affirms the fact, grounded upon nume- 
rous experiments on the helices; but, as takes place in all 
such cases, many other authors have denied it, and founded 
their opinion equally on the basis of experiment. 
The experiments of Trembley on the green hydrz, or fresh- 
water polypi, have established beyond a doubt, that in this 
degree of organization, an animal can reproduce not only the 
different parts of its body, but that when the latter is cut in 
pieces, each piece can become a perfect animal. He even 
succeeded in causing six or seven heads to sprout from a 
single body, by dividing the latter longitudinally into so many 
strips. 
Bonnet, desirous of repeating the experiments of Trembley, 
and not being able to procure any of these green hydre, tried 
whether some fresh-water worms, a species of nais, could not 
