712 INFECTIOUS DISEASES. 



The observations made by the veterinary officers of the Board 

 of Agriculture caused them to doubt whether there was any disease 

 of the lungs of pigs which, in the absence of lesions in the intes- 

 tinal tract, could be accepted as evidence of swine fever. 



The bacillus which produced swine fever when introduced in the 

 healthy pig did not induce any special disease of the lungs. 



Pathology and morbid anatomy. Swine fever, like typhoid fever 

 in man, is essentially a disease of the digestive system, its chief 

 characteristic being certain morbid changes of a well-marked nature 

 which are found upon the surface of the mucous membrane in some 

 part of the alimentary canal. 



The changes referred to consist of what have been commonly de- 

 scribed as the formation of a series of ulcers, single or confluent, dis- 

 tributed upon some part of the intestinal tract, varying in size and 

 shape, of a yellowish-grey to black colour, and assuming as a rule 

 a circular form. In some instajices the lesions consist of diphtheritic 

 exudations with necrosis of the lining membrane of the bowels. 



These ulcers or necrotic patches may be found upon the tongue, 

 tonsils, epiglottis, stomach, and small intestines, but they are more 

 constant in the large intestines, especially the caecum and colon. The 

 lesions may involve the whole thickness of the mucous membrane, 

 but seldom penetrate the other coats of the intestine ; in fact, perfora- 

 tion of the peritoneal covering of the bowel is very rare in even 

 prolonged cases of swine fever. 



In cases where swine fever assumes the more acute form and 

 death supervenes rapidly, it is usual to find that the small intestines 

 are largely involved. 



In the non-acute or slowly progressing form the lesions are more 

 abundant in the large intestines, and in some instances the walls of 

 the intestines become so thick as a result of infiltration into their 

 structure and the excessively thick deposits upon the lining mem- 

 brane, that it becomes a matter of surprise that the passage of the 

 ingesta has been possible and that the animal has lived so long. 



Next to the intestinal lesions the congested condition of the lym- 

 phatic glands, especially those of the mesentery, may be considered 

 as most prominent among the pathological changes which occur in 

 swine fever. Occasionally centres of necrosis are observed in the 

 liver, and some writers refer to changes in or upon the spleen and 

 kidneys. 



The only lesions which can be characterised as absolutely typical 

 of swine fever are those present in the bowels, the absence of which 

 will justify any observer in declining to accept the case as one 

 of swine fever without some further evidence or inquiry. It must. 



