In the description of what occurs in inflam mation, reference was made to the fluid that exudes from the vessels and plays so large a part in the swelling of the inflamed region. This exuded fluid, it is highly probable, is not without its uses. It probably contains sub stances in volution unfavourable to the in , vading organisms, and, by bathing the injured or irritated tissue, the fluid may hinder to some extent continuance of the irritation, as well as dilute the poisonous material which has reached the tissue.
Au inflamed region of the body, specially if the cause of inflammation is a dirty or poisoned wound, may then he said to be the battle ground between invading septic organisms and defending white blood-cells, and the white cells defend in two ways : (1) by rendering the region of attack unfit for the invaders to live in, by discharg ing into the fluid that bathes it material they produce, or (2) by boldly issuing forth from the blood vessels in myriads and eating up the iu vaders.
It appears that one set of white cells in par ticular has the duty of preparing and discharg ing, when required, this protective material, and another set has the duty of eating up the invader.
In performing these duties both sets of cells may be sacrificed in large numbers. The poison may be so virulent as to destroy the cells, at least those that first reach the area of attack. But many of the cells thus early on the scene will be those whose destruction and breaking down liberates material unfavourable to tire life of the invader, and so even by their death will they protect the tissue by diminishing the activity of the assailant. Ultimately the energy of the invaders will thus be so reduced that they are a ready prey to the phagocytic cells that now fall upon them and quickly swallow them up.
It undoubtedly happens that many of the phagocytic cells, too, are unable to destroy the organisms they consume. It does not, therefore, always follow that organisms that have been picked rip by cells are deprived of their power of mischief. The cell may be till able to kill and digest them. Instead, they may kill the cell which has swallowed them, and, again liberated, become agents of mischief.
In various parts of the battleground, there fore, varying fortunes will prevail, the defending cells triumphing here, the attackers there, and what the ultimate issue is will frequently de pend upon the ability of the body to send con tinually fresh supplies of active white cells to the scene of conflict, or will be conclusively by the invading organism being so virulent as to paralyse all defence at the seat of attack, and being able to push its hosts in wards till the whole constitution is attacked and impaired.
The Results of Inflammation, it will be easy, from what has been said, to perceive, will vary— Firstly, according to the nature, intensity, and duration of action of the irritation, Secondly, according to the vigour and per sistence of the reaction with which the body in general resists the irritant.
Thus, in some persons of weak physique and flabby constitution, the same irritant may in duce a prolonged and extensive process, slow to cease, which in a person of vigorous con stitution induces only a slight and temporary disturbance. Upon the same circumstances also will itdepend whether the inflammation remains a merely local disturbance, however severe, or ends in a general and constitutional disorder.
Where the irritation is slight, the changes that have been described are little marked, the dilatation of vessels soon passes off, the cells that have escaped from the vessels and the exuded fluid disappear from the affected tissue, passing, with any that may have been destroyed, into the lymphatics, the drainage channels that exist in every tissue, and nothing is left to mark the Occurrence.
This is called resolution.
This restoration of the tissue to the normal occurs after more intense degrees of irrita• tion, but the irritation and the inflammatory proces's it provokes cannot pass a certain degree without some destruction of the ele ments of the tissue that has been attacked. These destroyed elements break down and are removed, but the healthy cells of the tissue proceed to replace the destroyed material by a growth of new cells, which gradually become transformed into fine fibres. These fill up airy gaps, so to speak, that have been caused in the tissue. They gradually shrink, forming a firm fibrous band, or bundle, or mass, marking the spot where the damage has been done. This is called a scar or cicatrix. It replaces the tissue that has been destroyed, but it never becomes converted into the same str acture that it replaces. On tire surface of the body the place where a sore has been, or wound, or burn, is always marked by the spot, or line, or irregular mark, different in colour from the rest of the skin, less elastic. In internal organs the same thing occurs. In examination of the bodyafter death it is always possible to tell where inflammation leading to permanent damage of any extent has occurred in any of the organs— heart, lungs, liver, kidney, stomach—by the pre sence of such bands, or masses, or patches of scar tissue.