ELEVENTH ANNUAL YEAR BOOK— PART X 559 



communicable to man, there is danger of anthrax, septic infection and 

 tuberculosis. 



First notice the skin which may be red or purple, then lay the hog 

 on its back and make an incision through the skin and muscles from the 

 anus along the median line to the throat, laying open the thorasic and 

 abdominal cavities for examination. In peracute cases the lesions are 

 very similar to hemorrhagic septicaemia with hemorrhages in any or 

 all of the tissues accompanied by inflammation of the intestinal tract. 

 The lungs may show various stages of congestion, areas of hepatiza- 

 tion and fine petechia on their surface, the latter being most character- 

 istic lesions in the lungs of hog cholera. The heart may show hemor- 

 rhages in the pericardium, endocardium and myocardium. The lymphat- 

 ics of the thorasic cavity are dark and congested. The lining membrane 

 of the chest cavity or pleura may show petechia, and occasionally 

 adhesions to the lungs or the walls of the chest cavity are observed. The 

 muscles of the abdomen may show fine hemorrhages, and in subacute 

 cases the intestinal tract shows the most pronounced lesions. The 

 stomach is first to be examined which may show intense inflammation 

 of its mucosa with diphtheritic or necrotic areas. The colon is generally 

 most prominently affected, and often can be noticed through the walls 

 without opening, and is the location of the button-like ulcers of hog 

 cholera corresponding in their location to the solitary lymph folicles 

 of the intestinal tract. The ileo caecal valve is generally the seat of ulcers 

 which are considered, when found, pathognomonic of hog cholera. The 

 mucosa of the small intestine is inflamed and may show necrotic or 

 diptheritic changes in its lining. The mesentary, or membrane which 

 suspends the intestines, is congested and its lymphatic glands stand out 

 as dark purplish nodules. The peritoneum, or lining membrane of the 

 abdominal cavity, may show fine hemorrhages and deep seated button- 

 like ulcers on the colon may extend to the serosa and result in septic 

 peritonitis. The kidneys are covered with hemorrhages varying in size 

 after the peritoneal covering has been removed. The kidney is also 

 darker in color than normal. The mucosa of the bladder may show 

 petechia and intense inflammation with hemorrhages which accounts 

 for the slightly blood stained urine, which is sometimes passed. The 

 body lymphatics do not become affected as do the visceral but the in- 

 guinal, cervical, sublumbar are generally larger than normal and slightly 

 congested. 



IMMUNITY. 



The rapid advances made in the study of immunity during the past 

 few years render it essential that we consider a few of the basic prin- 

 ciples upon which the serum immunization against hog cholera rests, 

 before describing the process. 



Immunity is that condition in which an individual or species of animal 

 exhibits unusual or complete resistance to an infection for which other 

 individuals or species show a greater or less degree of susceptibility. 

 Consequently it is only in connection with infectious diseases that we 



