152 DISEASES OF SWINE 



picture is found, with no ulceration of the bowels, and no spots in 

 the kidneys, it is often hard to make a diagnosis between the two 

 diseases, cholera and pneumonia. 



However, if we examine closely, we will usually be able to find 

 a few hemorrhagic spots in the kidneys, and also perhaps in that 

 portion of the lung not involved in the pneumonia changes. In 

 some cases the signs of cholera are so few, and the appearances in 

 favor of pneumonia so strong, that it is necessary to resort to 

 laboratory tests with the blood, and injection of the suspected 

 blood into healthy susceptible pigs in order to arrive at a diagnosis. 

 Often examination of the carcass of a second animal from the same 

 herd will reveal changes more typical which will enable us to clear 

 up the diagnosis. 



Other Lesions in the Thorax.— Closely associated with the 

 lungs we have the lymph-glands of the thoracic cavity, especially 

 important being the bronchial and mediastinal glands. In cholera 

 these glands share in the hemorrhagic lesions described in the other 

 lymphatic structures of the body. The hog-cholera virus appears 

 to have a special tendency to attack the lymphatic glands and 

 produce severe hemorrhages in them. Accordingly, we will find 

 these glands swollen, discolored with blood, and, if examined under 

 the magnifying powers of the microscope, with dilatation of the 

 blood-vessels and clotting of the blood outside the ruptured blood- 

 vessels. 



The pleura, or lining serous membrane of the chest cavity, is 

 also usually the seat of quite marked change in severe involvement 

 of the thoracic cavity. There is a loss of the normal shiny appear- 

 ance of this membrane, and it becomes dull and opaque, resembling 

 very much in appearance a tarnished mirror. Beneath its surface 

 we find frequently small pin-point-sized areas of discoloration. In 

 some cases these are very marked, and the membrane is freely 

 dotted with hemorrhage. These genuine hemorrhages can be 

 readily distinguished from blood accidentally spilled on the pleura, 

 as by cutting a small vein. If it is simply spilled blood, it can be 

 readily washed off with water, while, if it be due to genuine hemor- 

 rhage into or beneath the pleura, it remains after washing, being 

 within the tissue rather than upon it. 



