240 ON THE EARLY STAGES OF INFLAMMATION 
Thus we may, I think, regard it as fully established, that, in mammalia as 
well as in amphibia, both the red discs and the colourless globules of the blood 
are completely free from adhesiveness within the vessels of a perfectly healthy 
part, but that when the tissues have suffered from irritation, both kinds of 
corpuscles assume, in proportion to the severity of the affection, a degree of 
that tendency to stick to one another and to neighbouring objects which they 
possess when withdrawn from the body, and consequently experience obstruction 
to their progress through the minute vessels. 
And here I cannot avoid remarking, that this principle explains, if it does not 
altogether reconcile, the discordant opinions of physiologists regarding the 
causes of the circulation. It shows that while there is, as we have before seen,}! 
strong ground for agreeing with those who hold that the flow of the blood is 
due simply to the contractions of the heart, aided, in animals with valved veins, 
by the actions of the muscles, the respiratory movements, and, in the case of 
the bat’s wing, by rhythmical venous contractions ; yet there is also much truth 
in the view of those who maintain that the tissues of a part, independently of 
any change of calibre in the vessels, exercise a great influence upon the progress 
of the blood through the capillaries. For though the tissues do not, as has been 
hitherto supposed by the latter class of authorities, actively promote the circu- 
lation, yet their healthy condition is none the less necessary to it, being essential to 
the fitness of the blood for transmission by the heart through the minute vessels. 
It is an interesting question, whether the freedom of the corpuscles from 
adhesiveness in health is due to some active operation of the tissues upon the 
vital fluid, or whether their adhesiveness in an inflamed part or outside the body 
is the result of a prejudicial influence exerted upon the blood by the irritated 
tissues, or by the objects of the external world with which it comes in contact 
when shed. The fact that the non-adhesiveness of the corpuscles within the 
vessels continues in an amputated limb, shows that it is independent of the 
central organs of the nervous system, and probably too of any nutritive actions 
going on in the tissues. Also, if the latter were concerned in its production, 
we should expect to find the corpuscles adhesive in the large arteries and veins 
of the webs, since it is doubtless chiefly in the capillaries that the mutual inter- 
changes take place between the blood and the solid elements of the body. It 
may be difficult to obtain further evidence upon this point, but some light may 
be thrown upon it by the consideration of the causes of the coagulation of the 
blood, which seems to be a closely allied subject. 
of the frog when I have used a plate of thin glass in the same manner as with the bat, for the purpose 
of applying a high power to the pigmentary tissue. 
* See p. 220. 
