500 ACTION OF STIMULANTS IN CONGESTION OF THE LUNGS. 
pathologists would advise stimulants, the other would em¬ 
ploy revulsives; one would endeavour to drive onward the 
obstructing mass of blood, the other would seek to divert 
the current and thus relieve the distended organ from 
pressure. 
Obviously the first thing to be settled in this controversy 
is the precise nature of congestion, and, if possible, it is 
further required to determine what is its natural process of 
cure. The phenomena of congestion may be observed very 
easily in any transparent part of a small animal under the 
microscope, and the most remarkable thing which is noticed 
is the entire absence of effort on the part of the healthy 
vessels to overcome the obstruction. The blood in the con¬ 
gested part remains nearly stationary, or is affected only to 
the extent of a slight oscillation; the vis a tergo meanwhile 
seems to be a very insignificant force, scarcely increasing the 
amount of oscillation in the stagnant fluid, and the stream of 
blood which fails to effect a passage in the intended direction 
always, after a few attempts to proceed, finds new channels, 
and adds little or nothing to the accumulation. 
By and by the extreme vessels of the congested part are 
relieved of a portion of their contents, which glide away into 
previously unseen channels, and gradually the mass is less¬ 
ened, not by the pressure from behind driving on the mass 
of blood, but apparently by the spontaneous forward motion 
of the stagnated fluid. What strikes one, in watching the 
various movements of the blood in the capillaries, is the 
seeming independence of all the actions. Judging from 
what is commonly stated about the circulation, it would 
be expected that all the blood-corpuscles would be driven on 
heedlessly, in obedience to the impetus communicated from 
the heart; but so far from this being the case, each corpuscle, 
or column of corpuscles, in the capillaries, seems to be 
making efforts to pass in one direction, and, failing in this, 
seeks a new one, altering form and arrangement in accord¬ 
ance with new conditions, and altogether behaving quite 
otherwise than as passive agents under the influence of a 
resistless impulse. 
The observation of the whole process is rather provocative 
of doubts in the mind of the inquirer than suggestive of 
explanations. But one thing is clearly apparent, viz. the 
incapacity of the current of circulation behind a congested 
part to greatly increase or diminish the morbid condition, 
which remains simply uninfluenced by the force of the pres¬ 
sure, and only ceases when the contents of the circumferent 
vessels find an exit. 
