Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
difficulty of defining the term Adventitious 
Product with precision has so frequently been 
acknowledged, that we feel extremely diffident 
in offering a new attempt to the consideration 
of morbid anatomists ; the more so as the re¬ 
cent disclosures of the microscope would pro¬ 
bably strike the generality of persons as 
having, almost of necessity, simplified the 
task, while they have in reality rather in¬ 
creased its perplexity. Fully conscious, then, 
of the debatableness of the ground we tread 
on, we would apply the term Adventitious 
Product to any substance which, either pro¬ 
duced by or developed in connection with the 
animal frame, - neither forms a natural consti¬ 
tuent element, nor a natural secretive product, 
of the structures amid which it is evolved. The 
qualification, “ either produced by or deve¬ 
loped in connection with the animal frame ” is 
required to ensure the exclusion of Foreign 
Bodies ; and the latter member of that quali¬ 
fication, “ developed in connection with the 
animal frame,” as plainly necessary to ensure 
the inclusion of Parasites, which (whether 
they be the proceeds of equivocal generation 
or evolved from germs introduced from with¬ 
out) are certainly not produced by the textures 
containing them. 
Understood thus, (and the signification 
seems the widest that can, in a practical point 
of view, be given to the term,) the character 
of adventitiousness is conceived to arise in 
three different ways: — a substance may, in 
truth, be adventitious, because its nature is 
different from that of any of the natural tex¬ 
tures and secreted materials ; or because the 
form it has assumed differs from that under- 
which it naturally occurs j or because the situa¬ 
tion it occupies is one to which such substance 
is in the natural order of things wholly foreign. 
Thus tuberculous matter is adventitious, be¬ 
cause it differs in nature from all the elementary 
structures and secretions ;• a calculus com¬ 
posed of lithate of ammonia is adventitious, 
because the form, assumed by the salt compos¬ 
ing it, differs from that it wears as a constituent 
of healthy urine ; and an ossification of the 
pleura is adventitious, because the ossiform 
structure forming it occupies a locality in 
which, in the healthy state, bone is unknown. 
The amount of adventitious quality in pro¬ 
ducts of these three kinds differs : it is greatest 
and most clearly defined, where dependent on 
the nature of the constituent material. Thus, 
in the first place, concerning the adventitious¬ 
ness of cancer or pus, no doubt can ever arise ; 
their physical and chemical characters and their 
essential nature are decisive of the point. In 
the second place, when a product becomes ad¬ 
ventitious sifbply from the peculiarity of its 
localization, the question is often less clear ; 
nor indeed can it in the existing state of know¬ 
ledge be invariably settled. Muscular fibres 
have, for instance, been met with in the walls 
of the ureter ; albumen is excreted in great 
quantity with the urine in certain states of dis¬ 
ease: but whether such muscular fibres are to 
be considered evidences of hypertrophy or ac¬ 
tual new products, and whether such albumen 
must be viewed as a totally new material of 
renal secretion, or as a natural element of urine 
in excess, depends upon the mode of decision 
of the preliminary questions, whether rudimen¬ 
tary muscular fibres do or do not naturally exist 
in the situation referred to, and whether albu¬ 
men do or do not, in excessively small propor¬ 
tion, form a natural constituent of human urine. 
And this is not the only aspect under which it 
becomes practically difficult to distinguish hy- 
pertrophous from adventitious products. The 
two states are in some conditions of disease 
distinctly and intimately associated. Thus, in 
eburnation of the heads of bones, the proper 
osseous tissue undergoes hypertrophy only, 
while the adjacent articular cartilage becomes 
infiltrated with adventitious bone. Again, the 
fat, which forms in abundance in the liver in the 
so-called “ fatty degeneration ” of that organ, 
is at first merely an excess of that naturally 
existing in the hepatic cells, and can there¬ 
fore only be regarded as a product of unhealthy 
supersecretion : but with the advance of the 
morbid change, the inter-cell texture of the 
organ becomes infiltrated with fat ; and this fat 
is an adventitious product by reason of the lo¬ 
cality it occupies. Nature here, as elsewhere, 
transgresses the artificial limits established for 
the facilities of study. In the third place, it is 
clear that newness ofform implies the quality 
of adventitiousness in an inferior degree only 
— that a material naturally existing dissolved 
in a secreted fluid, for example, does not, when 
from physical or chemical causes it accumulates 
in solid masses, possess the quality in question 
to the same amount as another which is never, 
under any shape nor even in the minutest pro¬ 
portion, a natural existence. 
The great number and variety of the objects 
to which the term Adventitious Product, de¬ 
fined in the manner we have just proposed, 
will apply (from a microscopical crystal, for 
instance, to the highest species of intrinsically 
vegetative Growths) render it necessary, in 
limine, to introduce some order into the sub¬ 
ject. We shall consequently set out by tracing 
those lines of distinction which separate from 
each other the various objects united together 
by the common property of Adventitiousness. 
It would, no doubt, be desirable and most 
strictly logical to employ some one uniform 
principle in establishing the various divisions 
and subdivisions of this, as of all other groups 
of natural objects, which require classification. 
But in the present state of know ledge, at least, 
systematic accuracy of this kind is unattainable. 
Neither the anatomy of texture or of form, the 
physical or chemical nature or properties of 
ultimate elements, the mode of formation, the 
physiological properties, nor the pathological 
influences of morbid products, will, taken 
singly, supply a feasible instrument of classifica¬ 
tion. All must by turns be made to contribute 
their share in the work. And as all previous 
modes of arrangement have been found to 
bear the impress of contemporary physiolo¬ 
gical doctrines, so will the existing impulse 
towards micrological study be traced in ours. 
F 4


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