INTRODUCTION. 
XI 
discharged by the mouth, in the same manner as birds of prey disgorge 
indigestible substances: though many of them are ground down, by the 
powerful action of the gizzard, mix with the food, and pass through the 
vent. To prove the power and strength of these muscles, and to demon- 
strate, that the trituration of grain, in the gizzards of granivorous birds, 
is solely the effect of powerful pressure, and violent percussion, the 
indefatigable Spallanzani made many curious, but at the same time, cruel 
experiments. Aware, that smooth and blunt substances, are not injurious 
to the gizzards of birds, his active mind led him to discover the conse- 
quences which would arise from the introduction of sharp, lacerating 
bodies. At first, he gave to a cock, several fragments of broken glass, 
(each about the size of a pea,) and wrapt up in paper, that they might 
not v/ound the oesophagus, in their passage to the stomach. When nearly 
twenty-four hours had elapsed, the animal was killed ; the sharp angles of 
the glass had become obtuse and blunt, and the fragments liad lost in 
weight twenty-four grains. On examining its gizzard, he found it 
glittering with innumerable, vitreous particles ; but when, at another time, 
he inclosed those little pieces of glass in tubes, and caused them to be 
swallowed by a turkey, and an hen, and left a similar period in their 
stomachs, they were taken out, with their edges as keen, as when they 
were introduced. On the examination of the stomachs of the cock, and> 
of two wood pigeons, to which he had given points of glass, he says, that 
there was no laceration, no division, not the smallest jagged appearance. 
Their stomachs were in every respect the same as those which had not 
afforded reception to any unusual substance. Surprized at the fact, he 
proceeds with experiments, apparently still more dangerous. Twelve 
small lancets, with sharp points and edges, fixed in a ball of lead, were 
given to a turkey, and left in its stomach eighteen hours, which was then 
opened, but nothing appeared in the gizzard but the naked balls, the twelve 
lancets having been broken to pieces, and three of them were found in the 
intestines, pointless and blunted ; yet the stomach remained sound and entire. 
By repeated trials, he discovered, that the edges of these sharp instruments,, 
c 2 
