C 361 3 
XV. Account of a Tumour found in the Substance of the human 
Placenta . By John Clarke, M. D. Communicated by the 
Right Hon. Sir Joseph Banks, Bart. K. B. P. R. S. 
Read May 17, 1798. 
hilst the structure and uses of any part of the animal body 
remain unknown, every new fact or occurrence ought to be 
recorded ; since, by this means only a more perfect knowledge 
of it can be expected to be obtained. 
As there are few subjects more interesting than those which 
concern the functions of animals, and more especially those 
processes by which they are originally formed, and afterwards 
sustained, I beg leave to submit the following Paper to the at- 
tention of the Royal Society, supposing it not to be foreign to 
the general views of the institution. 
The exertions of the most patient industry have been hither- 
to baffled, in the attempt to detect the first changes which suc- 
ceed that process by which animals are propagated. 
If the object of immediate pursuit has not been obtained, 
much light, in the course of the investigation, has been col- 
laterally thrown upon the growth and nutrition of animals, both 
in the egg state of oviparous animals, and in the uterine state 
of such as are viviparous. 
The structure of the egg of oviparous animals serves to eluci- 
date the corresponding process in the viviparous ; and, although 
in many cases analogies are very inconclusive, yet in this the 
mdccxcviii. 3 A 
