When the changes in the epithelia are only slight and secondary, it is spoken of as an interstitial (lying between) inflammation, which strictly speaking denotes confined to connective tissue, and is therefore a term not entirely correct. When the inflammation of the epithelia is severe and may lead to their partial destruction, it is called a parenchymatous inflammation; that is, one involving the soft cellular substance. There is still another variety, the suppurative, which is the most intense of all, and indicates the production of an abscess and the entire destruction of the tissue implicated.

Beside these general grades of inflammation there are special sorts produced by specific micro-organisms. In all general inflammation we may expect to find such organisms, which in most cases belong to the class of micrococci, such as staphylococci and streptococci. In gonorrhea we have a special organism called the "gonococcus"; while in tuberculosis—a variety of inflammation in which the blood-vessels are completely destroyed and a change or degeneration called "cheesy" is produced, leading to the production of a tubercle—a rod-like bacillus is invariably found, the well-known and unfortunately too common tubercle bacillus. In syphilis—another special variety of inflammation—a specific micro-organism is also surely present, but of this microbe science has not as yet discovered the exact nature.

The question of the origin of tumors or new growths is also an extremely important one; and it is undoubtedly true that many tumors arise where there was a previous inflammation, this being especially the case in tumors of the rectum. Why such a growth should arise in some cases and not in others is as yet unknown, though microbes are held by many to play an important rôle.

When an inflammation has lasted for such a length of time that it has become chronic, a new tissue will sooner or later be produced in varying amount; and this newly formed fibrous connective tissue may entirely replace previous normal structures. Through the exudation and consequent changes in the normal tissue a large amount of mucus is at first secreted, but this secretion becomes less and less marked the more the inflammation causes a desquamation of the epithelia. Pronounced desquamation with new formation of connective tissue and no fresh exudation will, sooner or later, occasion dryness—this dryness being sometimes very pronounced. The longer the inflammation lasts, the severer it will be; and the greater the amount of tissue it attacks, the more will the normal tissue be destroyed and replaced by a new connective tissue. A partial destruction will cause shrinkage of the organ (so-called "cirrhosis"); while a complete destruction of certain parts will result in what is known as "atrophy" (a wasting away of normal tissue). In atrophy the blood-vessels as well as the original connective and epithelial tissue are destroyed; while the newly formed tissue leads to hypertrophy (excessive over-growth) of other portions of the organ. Such a hypertrophy must not be confounded with an induration that may be present later, or even at the very commencement of an inflammation, due to modification of the blood-vessels and surrounding tissues.

Chronic inflammation, sooner or later, leads to secondary degenerations, that is, new products of the protoplasm, the most common of which is fatty degeneration. In this form fat granules and globules arise, which are at first minute, later on larger; these in certain organs, such as the liver, may become so pronounced as to entirely replace the original tissue. Another degeneration—which, however, is found only in chronic systemic disturbances, such as tuberculosis or syphilis—is the waxy or amyloid degeneration, a peculiar chemical change the exact nature of which is unknown.

Various chemical changes are by no means uncommon.

An important question is the decision as to the length of time an inflammation has lasted; and this at best can be determined only approximately and after long experience. The older the inflammation, the more the connective tissue has developed; this connective tissue is at first soft, but soon becomes more and more dense; the result being a varying degree of hardness of the organs.

Again, secondary degenerations are more pronounced in long-standing processes. In comparatively fresh cases blood-vessels are still more or less numerous and the tissue appears red, while in older cases these vessels become completely obliterated, and the tissues take on a white, glistening color, becoming harder and denser as the years advance. If a process has lasted twenty or thirty years, the changes to the eye and touch are practically the same as after forty or sixty years.

The changes, as here described, will be the same upon any mucous membrane; and in the large intestine can be easily studied and are perfectly characteristic.

Rarely does an infant escape repeated attacks of inflammation of the integument of the anus and the mucous membrane of the anal canal. The inflamed integument is treated and healed, but no attention is given to the inflamed mucous membrane so that the inflammation in time becomes chronic, involving the rectum also. Should the infant be so fortunate as to escape inflammation (proctitis) of these organs during the wearing of the diaper, there are numerous other exciting causes of inflammation which it will not be likely to escape, hence the almost universal symptom of constipation among civilized people; and hence later in life you hear the familiar expression, "I have a touch of the piles," and many other complaints of bowel ailments that are usually the outcome of that deplorable inflammation.