REPORT OF MEDICAL SECTION. 148 
the organ, and the conditions by which it may be influenced in 
this respect ; also whether the nutrition resulting from the com- 
bined action of the vascular and nervous systems is steady or sub- 
jected to periodical or other variations. 
_. Although we are at present very much in the dark upon most 
of these subjects, we may be convinced from various examples 
that the characters of a secretion are influenced by the texture of 
the organ which produces it. In those adventitious cysts which 
are liable to be formed in different parts of the body, but which 
are most frequent as well as most distinctly formed in the ova- 
ries and in their vicinity, we find, that whilst they are of a thin and 
delicate texture the secretion is thin and aqueous or serous, but 
that when they have become a little thickened their secretion is 
thick, viscid, and mucous oralbuminous. A similar transition, 
but in a less marked degree, may be-seen in the serous mem- 
branes natural to the body, and also in the mucous membranes. 
Where these are thin and delicate, us in the case of the con- 
junctiva, and in the extreme branches of the bronchial tubes, 
their secretion approaches very closely to that of the serous 
membranes, whilst the thicker membranes which line the vari- 
ous portions of the alimentary canal produce large quantities of 
mucus. When chronic inflammation has thickened these mem- 
branes the quantity and viscidity of the mucus produced is noto- 
riously increased. 
_ In investigating the causes which operate in the production 
of animal secretions there are doubtless several points to be 
considered beside the chemical composition and anatomical 
structure of the parts producing them, and the composition of 
the fluid from which they are derived. Even after the secretion 
has been poured forth from the living solid, it is certain that it 
undergoes important changes by which its character is in many 
respects altered. Although these changes are in part to be 
ascribed to the material remaining under the influence of the 
living structure by which it is surrounded, and which may act 
both by abstraction and addition, nevertheless there are some 
modifications more immediately depending on the inorganized 
secretion itself. Such changes seem to be more particularly 
within the undisputed limits of animal chemistry in its present 
State, and we may reasonably expect to find their parallels or 
analogues in the changes which take place in dead matter apart 
from the living body. While some of these changes are un- 
doubtedly brought about by the influence of air and moisture, 
_by which the addition or subtraction of elements may be effected, 
in other instances the change seems to be more particularly 
Bs 5 
