DISEASES OF DOMESTIC AMIMALS. 9 



as congestion. Congestion is an excess of blood ia the parts. There are 

 various kinds of congestion. If there is too much blood in some parts, 

 it is local congestion, or partial plethora. We see this without there 

 being any disease Congestion can be caused in various ways, and 

 very easily, indeed. There is always more or less congestion in the 

 lungs in severe exertion. It can be induced by means of the nervous sys- 

 tem — as in anger, one person's face will get red, and another's will get 

 pale — or in the blush of a young lady; or this is sometimes seen in a 



bashful yonng man, as in Mr. , and see how quickly it takes place. 



It is done by means of the nervous system. If we irritate a part 

 mechanically, we give rise to active congestion. It may end in hemor- 

 rhage, or pass on to inflammation. It is difficult to say whether it 

 will pass into inflammation or not, especially in the lungs. 



Signs of Inflammation. — The visible signs are heat, pain, redness, 

 and swelling. But inflammation may go on to a great extent and the 

 tissues be considerably destroyed, without all these taking place. There 

 are signs by which it has been recognized, for hundreds of years. In 

 man, the sign first noticed, often is 



Redness, but it is not so in domestic animals, as the skin is covered 

 with hair. Eedness depends upon the amount of blood sent to the parts, 

 and it varies in difterent places, and according to the causes. If a horse 

 receives an injury in the eye, the mucous membrane is very much red- 

 dened ; and in scratches, redness is seen, especially if in a white leg. In 

 acute inflammation, the parts are of a florid colour, and it takes place 

 quickly ; if in the bowels, gangrene may take place quickly, due to 

 changes which go on in the parts The 



Heat is due to the amount of bloofi, and the changes being undergone. 

 If the tissues of the body are being broken up in any way, an effort is 

 made to take them from the system, and this produces heat. The heat 

 of a part is, however, not so much above the natural temperature as you 

 would suppose. In inflammation of the hock, joint, or foot, when you 

 apply the hand, you would suppose there was an increase of many 

 degrees, but it is not so much as you would think. In inflammation it 

 would run up to 102° or 104^^', so it varies from 98'^ to 104°. The increase 

 is greater remote from the heart, as the natural temperature of those 

 parts is several degrees below that of the blood at the heart. We flnd 

 this increase in the hock and foot. The temperature is sometimes higher 

 in influenza than in enteritis, so it is due in many cases to the change 

 taking place. 



Swelling is due to exudation and effusion into the tissues ; first, en- 

 gorgement of the vessels, which is followed by exudation through the 

 walls into the surrounding tissues. In some tissues swelling is a very 

 evident sign. It takes place quickly and to a great extent, and, no doubt, 

 in some tissues afford relief. In many cases it must not be looked upon 

 with any great degree of alarm ; in lymphangitis it is not a very danger- 

 ous sign. But if in other parts, as the mucous membrane of the 

 respiratory organs, it is more alarming, and may produce death very 

 suddenly, by interfering with respiration. And although this is one of 

 the recognized signs of inflammation, it will occur from other causes, as 

 the peculiar swelling of purpura, which is not due to extravasation of 

 blood, and not to inflammation. We find it also in tuberculor swellings, 

 and rupture of the capillaries. 



Pain is another sign. This varies much in different structures; in 

 some being most excrcuciating — in laminitis, for example. Here we 

 have an extremely vascular and sensitive structure, and the tissues being 

 covered with a hard, resisting hoof, makes it more painful. In inflam- 



