HUMAN AND ANIMAL VARIOLAS. 
327 
in size from that of a pea to a haricot-bean, ancl of a pale-red hue. 
Increasing in volume, a viscid yellow fluid appears beneath the 
epidermis. At first this fluid is in the centre, but it soon extends 
towards the circumference, giving the nodosities or papules a light- 
blue tint in the middle, but a reddish-blue or yellow color towards 
the periphery. At this period the centre is also usually utnbili- 
cated or depressed; the margin is hard, tumefied, and painful; 
and when the skin is thin and transparent, a red areola is 
noticed. These “pocks” gradually increase in dimensions, and 
towards the eighth or tenth day have acquired their maximum 
development. On the udder they are generally circular; on the 
teats they are oblong. The contents then become purulent in 
character, and a crust begins to form in the centre, gradually ex 
tending to the circumference. This crust is thick, shining, and 
deep brown or black in color; it is firmly fixed to the skin, 
from which it does not become detached until the tenth to 
the fifteenth day, unless accidentally removed. When it has 
fallen off, it leaves a cicatrix, which persists for a considerable time, 
and is at first bluish-red in color, but gradually becomes pale. On 
the udder the cicatrix is depressed in the centre. 
In the same animal there may be successive crops of papules 
and pustules ; they may not all be developed simultaneously, some 
being crusted, while others are only nodes. The latter eruptions 
may, however, be due to re-inoculation during milking; this is 
favored by the existence of sores or fissures on the teats. In conse¬ 
quence of this circumstance, the malady may not pass through 
all its phases within a less period than a month or six weeks. 
The lymph taken towards the eighth or tenth day is most active 
for vaccination purposes. 
The variable color of the vaccinal pustules is not an essential 
characteristic of the disease, and does not therefore indicate the 
real nature of the eruption. If the skin is fine and white, the 
variolse have a silvery-white, bluish-white, or slatey hue; if it is 
thin but dark colored, they are leaden-grey; if the hair is of a 
bright shade, they have a color varying from a bright-red to a 
pale or blood-red tint, but always wear a metallic lustre. On a 
thick, white, and wrinkled skin they have a dull opaline lustre. 
