50 PATHOLOGY. 



Such a classification as tlie above is merely intended to bring 

 before the student at a glance the variety of morbid material 

 which is concerned in the expression of many of these phenomena 

 seen in the course of disease, the distinctions made being mainly 

 based on structural analysis and microscopic examinations. 



It was formerly a much debated question whether diseases 

 had their principal seat in the fluids or solids of the body. At the 

 present time the purely solidist, as well as the purely humoral 

 principles, may be said to have died a natural death, and we can 

 only wonder how men could have advocated exclusively one 

 view or the other, and refused to allow that both solids and fluids 

 had their share in the production of morbid phenomena. That 

 many diseases are caused by the presence of a morbid material 

 in the blood, which of itself is perhaps the flrst to be modified, 

 there can be no doubt; at the same time it cannot be denied 

 that the tissue plays a most important part in the various 

 pathological processes which constitute disease. In pleuro- 

 pneumonia contagiosa, "for example, the blood is undoubtedly the 

 recipient of the contagium ; but it would be erroneous to suppose 

 that the operation of the morbid material was confined to the 

 blood alone, and that the exudation found on the pleura and in the 

 parenchyma of the lungs was a mere precipitation of a product 

 formed within the blood-vessels. In reality, the poison, though 

 taken by the blood to all parts of the animal frame, is limited 

 in its effects to the tissues of the lungs and pleura, and, like a 

 medicine which has special affinities, passes harmlessly over all 

 the other organs and structures of the body. In such an 

 instance the blood contains the cause of the disease, whilst the 

 solids of the parts affected are the seats of the diseased processes. 

 So it may truly be said that both fluids and solids are alike the 

 seat of the disease, that they are mutually dependent one upon 

 the other, that the solids are almost of necessity liable to be 

 affected by the fluids, and the fluids by the solids. 



In some diseases it is found impossible, w^ith the aid of the most 

 exact instruments, to detect any structural change, or the j)resence 

 of any of the morbid products already enumerated. Such diseases 

 are termed functional, whilst those in which an alteration of the 

 part can be detected are called structural or organic diseases. 



Functional derangement is undoubtedly due to an alteration 



