230 ANIMAL REPRODUCTIONS. 
ARTICLE IIl.—HALF THE HEAD REPRODUCED. 
We have feen that the conftituent parts of the 
fnail’s head are a fhagreen fkin, two lips and two 
mandibles, with a lunar tooth fixed in the upper 
one: the tongue ‘inferted into a femilunar carti- 
lage, part of an cefophagus; the brain divided in- 
to two lobes, and fending forth ten nerves, befides 
four horns of different fizes. Thefe practical re- 
marks, however, are fufficient to afcertain that our 
experiments, on the decapitation of thefe rep- 
tiles, have been corre€tly executed. If all the 
various parts formed a head fimilar to that of 
moft infects, I mean of a globular figure, or were 
comprehended in a part eafily diftinguifhed from 
the reft of the animal, one could at once fee where 
it began and ended ; confequently the exact place 
where the fciffars or knife ought to be applied. 
would be known without any hazard of error.. 
But the head of fnails is otherwife conftruéted : 
when out of the fhell, the body, if we omit the 
horns, is a rude figure of a cone, of lefs diameter 
before, and of greater behind, where confined by 
the opening of the fhell. It is a certain fa& the 
head exifts in the anterior part of the cone, but 
the difficulty confifts in afcertaining the precife 
portion which it occupies, that we may be fure 
how much it is fafe to cut off. To acknowledge 
the truth, no abfolute rule can be given, on ac- 
count 
