Foot and Mouth Disease. 319 



A most important question would be that of the virulence of the 

 milk, but inasmuch as the vesicles appear on the teats and even 

 on the openings of the milk ducts, and in bursting discharge their 

 contents with the milk into the pail, the milk becomes per force 

 infecting. The experiment of Hertwig and his students who 

 infected themselves by drinking the warm milk by way of experi- 

 ment, has been often repeated unwittingly by unwilling victims, 

 and the many cases of calves, pigs and chickens contracting the 

 disease by consuming the otherwise discarded milk leaves no room 

 for doubt that this product is often infecting. 



Among conditions contributing to a spread of infection, nothing 

 is more potent than a free movement of ruminants, and swine 

 whether determined by war, trade, or the intermingling of 

 different herds on commons or unfenced ranges. In infected 

 countries, in which cattle are distributed through large central 

 markets there is always a wide extension after one of these fairs, 

 the infection being narrowly circumscribed to herds receiving 

 cattle from the fair, or those that have travelled on the same roads 

 or fields after the market cattle. It has repeatedly happened that 

 cattle shipped from the United States, where this disease has long 

 been unknown, have been found diseased on their arrival at a 

 British port, simply because they have been tied upon the passage 

 with halters formerly used on infected Irish or Continental stock. 



Symptoms in animals. There is first a period of incubation 

 shorter in hot than in cold weather and varying from 36 hours to 

 6 days (exceptionally 15 days). It is altogether probable that 

 prolonged incubation is really delayed infection, the virus 

 having been attached to the feet for some time before it entered the 

 tissues. Cattle usually show the disease two days after exposure 

 in a public market, building or conveyance 



There is first moderate hyperthermia (102" to 103° F.), indi- 

 cated by the clinical thermometer before there is any outward 

 sign of ill health. There may be erection of the hair, tremors or 

 distinct shivering, dryness and heat of the muzzle, redness and 

 even tenderness of the buccal mucosa and teats, saliva drivels 

 from the mouth or may show as a frothy mass at the commissures 

 or margins of the lips, and there may be grinding of the teeth 

 and a peculiar smacking of the tongue and hard palate which may 

 be heard at a considerable distance. There are greatly impaired 



