The diseased conditions of the solid structures of the body, which are readily appreciable by the senses, are of two classes: First, those which are due to mechanical and chemical causes; and, second, those which result from abnormal vital action. The latter class may not be in the strictest sense primary diseased conditions, as little is known of the morbid vital action from which they result, but they may for the present, be so considered.

Under the first head may be included all kinds of surgical accidents, bruises, fractures, etc.; injuries from chemical agents as burns, injuries from caustics, or from irritating and corroding gases; the effects of gravitation, as in congestion of the longs resulting from the accumulation of blood in the lower part in certain weak states of the system when the patient lies continually on the back; the production of varicose veins in the lower extremities from long standing or walking; the effects of mechanical obstruction to the circulation, as from wearing garters, and tight-lacing, also from the pressure on the blood-vessels of enlarged glands and tumors of various sorts; the results of obstruction of the ducts of glands, as in obstrue tion of the biliary ducts; the resalts of interference with respiration, occasioned by mechanical obstruction of the trachea or oesophagus, or from pressure on the chest by tight-lacing, or malposition of the body.

Under the second class, that is, structural derangements due to abnormal vital action of various parts of the body, we may mention the following: Changes in the size of the organs, changes in their consistency, exudations, transudations, degenerations, morbid growths On account of the narrow limits of our space, we can delay but briefly on these various morbid changes, which of themselves furnish material for many large volumes. We must, however, hastily glance at a few of the most important. The changes in size of the organs are, of course, but two,-increase and diminution. Increase in size is termed hypertrophy. It is said to be either true or false, as the increase in size is due to the actual increased growth of the proper tissue of the organ, or to a mere expansion of volume without any actual increased growth of the tissue; as, for example, in hypertrophy of the heart we have sometimes an increase of size due to the increased growth of the hearts muscle, and at other times we have an increase in the size which is due to simple dilatation of its cavities and thinning of its walls without any actual increase in substance. In the majority of cases it happens that both forms of hypertrophy are present at once. Diminution in size is known as atrophy. In true atrophy there is a decrease in proper tissue. This may be accompanied either with an increase or decrease of size, since in some cases in which loss of proper tissue occurs, there is at the same time a great increase of size from the deposit of abnormal or adventitious tissue, the latter process being, in fact, in many cases the real cause of the atrophy.

Changes in consistency consist of hardening or softening. These changes may take place either with or without inflammation.

Certain fluids, when thrown out into the cavities of the body, or deposited in the interstitial spaces of the tissues, become solid or semisolid. These are termed exudations, in contradistinction from fluids, which, thrown out or deposited in this manner, remain in a fluid state, and are termed transudations. Exudation is a very common result of inflammation. Another solid or semi-solid deposit, which may be called an exudation, is tubercle, a characteristic product of consumption, or tuberculosis. Tubercles are said to be of two kinds,-the small gray tubercle, and larger yellowish masses of a cheesy consistency, called yellow tubercle.

There has been much discussion among pathologists as to which is the true tubercle. Probably the most correct view is that the two are simply different stages of the same morbid product, the gray tubercle after a time being converted into a yellow tubercle. More will be said on this subject in connection with the description of consumption. The peculiar deposit which takes place in a scrofulous enlargement of the glands, somewhat resembling tubercle, is also an exudation. Transudations give rise to dropsy or chlorosis, the former when the fluid collects within the closed cavities, the latter when the escaping fluid is discharged from the body.

Degenerations and morbid growths of various sorts are changes in the structure of organs resulting from mal-nutrition, which is probably due to a depressed condition of the vitality of the parts in which these changes occur. Under the head of degenerations is included what is known as fatty degeneration, in which the normal tissue of a part is changed to fat, as in fatty degenerations in the nervous system or in the muscular tissue of the liver, kidneys, heart-walls, blood-vessels, and, in fact, almost all the organs of the body. In some cases the proper tissue is absorbed, and a chalk deposit made in its place. This is known as calcareous degeneration, and frequently succeeds fatty degeneration. A peculiar form of degeneration of the liver, kidneys, and spleen, has been observed, in which the normal tissue of these organs resembles wax. This is known as waxy or lardaceous degeneration. Under the head of morbid growths are included various forms of cancer, fibrous tumors, and allied growths of a morbid character.