Foot-and- Mouth Disease. 99 



diseased animal into the lining membrane of the mouth is also 

 very effective, but injection of the virus into or under the skin 

 appears to be uncertain in its results. 



Course of the Disease and Symptoms. — As in other acute 

 contagious diseases an interval elapses between the moment of 

 actual infection and the time at which the first distinct symptoms 

 are exhibited. This is the so-called period of incubation. It 

 may be less than twenty-four hours when a large dose of virus 

 is injected into a vein, but it is very improbable that it is ever 

 so short in cases of natural infection. In the great majority of 

 cases in cattle it is from three to seven days, and it seldom or 

 never exceeds a fortnight. 



The first discoverable evidence of infection is a rise of 

 temperature, and this always precedes by some hours at least 

 any outward sign of illness. The thermometer will generally 

 show an elevation of 2 or 3 degrees Fall, at this stage, but soon 

 after the eruption appears in the mouth or on the feet the 

 temperature begins to fall. 



The end of the period of incul)ation is generally fixed by 

 the appearance of distinct symptons of illness, and in uncom- 

 plicated cases in cattle the disease from this point usually runs 

 the following course. 



The affected animal shows such general indications of 

 illness as dulness, shivering, loss of appetite, " staring of 

 the coat," and stiffness in movement. These premonitory 

 symptoms are followed by others which are characteristic of 

 the disease. The animal ceases to feed, and is reluctant to 

 move. From time to time it makes a peculiar smacking noise 

 with its lips, from which a more or less frothy saliva escapes. 

 If the mouth is opened, white blister-like elevations will now 

 be found on some part of the buccal mucous membrane 

 (Fig. 1) ; these soon burst and become converted into shallow 

 erosions (Figs. 3 and 4). When made to move the animal is 

 obviously lame or " tender on its feet " ; and while standing it 

 frequently shifts the weight from one leg to the other, and 

 shakes its feet as if to get rid of something adhering to them. 

 This tenderness of the feet is well-mai^ked even before the 

 formation of vesicles ; but these soon appear on the skin 

 between the claws, or on the posterior aspect of the hoof 

 immediately above the horn. When the vesicles in the 

 mouth have burst the animal suffers increased pain, rumina- 

 tion ceases entirely, and all food is for a time refused. 

 In consequence of reflex irritation there is a copious secretion 

 of saliva, much of which, from the pain of deglutition, is 

 allowed to trickle from the mouth. The general appearance 

 of the animal is now indicative of great depression — the eyes 

 are dull, the ears drooping, the back arched, and the hair erect 



E 2 



