244 Mr. Gibbes on the Conversion of 
<e external membrane, and likewise the pleura, being greatly 
“ thickened, and converted as it were into a white crust, like 
“ melted tallow grown cold.” In a note he says, “ I am now 
“ doubtful if this crust was the pleura and external coat of the 
“ lungs, changed from a natural state by soaking in a puru- 
“ lent fluid, and if it was not altogether a preternatural sub- 
“ stance, formed by fluids deposited on those membranes, and 
“ compacted together by the motion of the lungs.” 
Much has been said by many authors .on the subject of se- 
cretion. It was at one time supposed that it depended on some 
peculiar property of the living principle ; and it was thought 
impossible to form any secretion but through the medium of 
secreting organs. M. Fourcroy has, however, contradicted 
this by the experiments where he forms bile. 
Spermaceti is an animal substance, secreted in a particular 
species of whale, and the substance which is formed in the 
foregoing experiments, as far as I can judge, agrees wdth it in 
every particular. 
M. Fourcroy says, that M. Poulletier de la Salle 
found a crystallized inflammable substance similar to sperma- 
ceti in biliary .calculi. 
May not the suety matter in steatomatous tumours arise 
from something of this kind ? 
By attending to the various secretions of the body, by exa- 
mining their composition in the healthy and morbid states of 
the system, may we not expect to derive great advantage, par- 
ticularly when accurate experiments are applied towards the 
relief of disease ? 
Some excuse may perhaps seem necessary for the little at- 
tention which has been paid to the accurate results in the 
