ROYAL VETERINARY COLLEGE. 
643 
task, even for an individual wholly devoted to the elucidation 
of the subject. Such, however, is neither my intention nor 
desire, my object is only to point out the practically im- 
portant services that may be rendered by the microscope, 
and by the science of chemistry, in the examination of the 
various fluids in the body, whether in their healthy or dis- 
eased states. The relation of this inquiry to the science 
of pathology is, I think, beyond question. It is evident that 
healthy secretions can only be formed by the organs of a 
healthy being, and it is, therefore, a matter of great interest 
to be able to discover, whether or not the variations met 
with in these secretions are of a nature which will permit 
of our establishing any connection between them and peculiar 
diseased conditions of the constitution, or in the nature of 
the tissue affected ; there can be no doubt, that the in- 
tegrity of the blood, bloodvessels, and tissues, is essential 
to the due performance of healthy action, and it becomes 
a special object to discover, in case of local disturbance, 
the seat of error, that the appropriate remedies may be ap- 
plied, in the one instance, through the constitution, and, 
in the other, locally to the affected tissue. It is well esta- 
blished, that so close a connection exists between the vital 
powers, which may be considered as the centre or focus of the 
animal economy, and the tissues or periphery of the body, 
that scarcely any disturbance can occur to the one without 
the other becoming simultaneously affected. Sometimes, how- 
ever, it is extremely difficult to discover from which source the 
first cause of the diseased action arises; for instance, a local 
injury may prove an exciting cause of a malignant develop- 
ment, and yet it is well established, that such a disease can 
only be excited in a constitution already predisposed to it, 
and that no isolated local malignant action can exist ; so that a 
blow, or any other local exciting cause, can only be looked upon 
as the source of the development of a disease already inherent 
in the constitution. Another instance may be given of the 
difficulty which may arise in attaching the source of the disease 
to the constitution, or to the local injury. A person may re- 
ceive a blow on the back, which may give rise to the formation 
of an abscess; if such an accident happen to a patient of a 
strumous diathesis, the bones of the spine are liable to become 
affected, and lumbar abscess will be the consequence. Without 
any such exciting cause, however, a lumbar abscess may form 
from an idiopathic deterioration of the spine. Now it becomes 
a matter of the greatest importance to ascertain, whether the 
abscess in question results from the mere local injury, or from 
an inherently defective constitution, as, in the former instance, 
