A CONTRIBUTION. 
145 
tenacity. I must also mention that in France the variola of the 
turkey, which probably should be classed here, has often been 
looked upon as the cause of v. ovina. 
Variola vaccina .—As to its seat: we find vaccina as a local 
exanthema, as a rule, upon the teats; less frequently, concomi¬ 
tantly upon these and the udder; exceptionally, it is limited to 
the ndder alone. Y. vaccina distinguishes itself sharply from 
other forms in that it comes to pass almost always by female 
animals, and by these only upon the udder, and during lactation. 
After an incubation’s stadium of three, four, six days, we see the 
development of the characteristic pustules following on a stadi¬ 
um of hyperamia, tumefaction, noduloi, and bulhu development, 
and completing their course in from five to six, less frequently 
in from eight to ten days. The number of variolse is generally not 
extreme ; it is seldom that we find twenty to thirty present at one 
time. The variolm are generally lenticular to pisiform—some¬ 
times larger, to two cen. in diameter—generally of a round form, 
the centrum somewhat indented; sometimes, however, the umbo 
entirely fails, or is only slightly intimated, or in the centrum we 
simply find a dark point; in other cases the variola is slightly 
elevated, conical or accumulated. Frequently the variolfe, as 
such, present nothing characteristic, are quite flat, and entirely 
without the pit; the entire process is so unimportant that it may 
be easily overlooked. The finer construction is similar to the 
human variola. That the variola) have interiorly a retriculated 
structure is easily to be perceived, as upon puncture we are never 
enabled to remove the whole contents, but must press the same 
out. In the virulent stadium the contents is clear and colorless, 
later purulent and no longer infectious. 
The color of the vaccine variolce is on the one side determined 
by the stadium of efflorescence , on the other side by the color of 
the udder. While on the light udder of white or light colored 
cows the variolm appear bluish-white and pearl-white, we find 
them yellowish in color on the dirty yellow colored udders of 
dark cows. Sometimes the variola) have a silver lustre, lead-gray, 
amber color, or the lustre of mother-of-pearl. The especially 
peculiar silver or mother-of-pearl color, comes frequently only 
