LIVE STOCK AND BREEDING 99! 



tongue, while the virus does not pass into the blood, which still retains a 

 sufficient degree of immunity to prevent general infection, or else it enters 

 the blood for a very short time and in an attenuated form only. These are 

 the cases when the feverish reaction does not take place or only amounts 

 to a few tenths of a degree for a brief period. 



The chnical forms of foot and-mouth disease (external, internal or 

 malignant) are in direct relation with the fluctuations in the degree of im- 

 munity existing in the local tissues and the blood. When the animal has 

 never had the infection, or has completely lost the internal or local immunity- 

 produced by a previous attack of the disease, the slightest injury to the epi- 

 thelium of the tongue and the rumen (for instance, injuries caused by the 

 heads of rye-grass, in the presence of the virus) suffices to produce a first 

 focus of the disease, which in a few hours causes the infection of the blood, 

 marked by the onset of fever. When on the other hand, as frequently 

 occurs, after an attack of foot-and-mouth disease, some degree of immunity' 

 still continues in the blood, the seat of disease involving one or more points 

 of the epithelium of the entrance to the digestive passages remains localis- 

 ed but the \'irus may, in this first passage, acquire an increase of infective 

 activity for other susceptible animals, 



7) Therefore, in the production of immunity against the malignant 

 virus of the disease, i. e. the one with the maximum of infecting and spread- 

 ing power, the writer preferred to combine the products of local lesions with 

 those of the blood in order to utilise the substances elaborated by the virus 

 in the tissues for which it exhibits a preference, and obtain an enhancement 

 of local histogenic immunity in order to secure a lasting and sure prevention 

 of external lesions. The latter, even if slight, may have serious conse- 

 quences, owing to the occurrence of secondary symptoms or the spread of 

 the virus through the bod}'. 



In the lesions of the epithelium, substances are observed which may be 

 termed granido-stinmlines and granulo-ly sines, inasmuch as they exert, 

 as a specific character, in the first place a positive chemiotaxy for the leu- 

 cocytes with eosinophile granulations, and afterwards a lithic action, which 

 results in an infiltration of the eosinophile granulations into the tissues of 

 the sick animal in direct ratio to the gravity of the infection. The charac- 

 ter of immunity is indicated by the cessation of the process of dissolution 

 of the eosinophile cells. 



8) In animals which have died from foot-and-mouth disease at a 

 late period, the virus may also not be present in the blood, but is found 

 localised in various organs, especially in the cardiac muscle, the brahi, 

 the liver and the kidney, less frequently in the spleen or the marrow. When 

 the virus is in the blood it is chiefly found in the venous blood, being in 

 largest amount and virulence in the portal vein. 



The bulk of the virus is eliminated from the blood through the kidney. 

 This elimination also occurs, though in a lesser degree, through the milk 

 and the saliva. In the majority of cases these only become infectious 

 owing to the products of local lesions. It can even be shown that the 



