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some nodules the excess of lymph raises the entire outer 

 layer of skin over the nodule, forming one large unicel- 

 lular vesicle, filled with thick, yellowish lymph (serum). 

 The vesicles usually become mature in 8 to 10 days, and 

 vary in size from one- fourth to three- fourths of an inch 

 in diameter; they are usually circular on the udder and 

 may be elliptical on the teats. When the vesicles are not 

 broken their contents become purulent (filled with pus), 

 the centre first becomes brown in color which soon ex- 

 tends to the border of the pustule. The pustule dries 

 and a dark brown scab or crust is formed which usually 

 drops off about the fourteenth day, leaving a pale red 

 or white and shining, depressed scar. The vesicles or 

 pustules on the teats are always broken by the milker and 

 the brown scabs come off prematurely and sometimes 

 drop into the milk to be removed from it by the strainer. 

 Complete recovery takes place in the eruptions that ap- 

 pear on the udder in about 21 days ; but with those on the 

 teats successive scabs or crusts are removed, ulcers be- 

 come "cracked" and raw, and healing occurs slowly, re- 

 quiring in some instances thirty to forty days. During 

 this time re-infection or infection with pus germs may 

 take i>lace and thus successive crops of nodules (pos- 

 sibly vesicles and pustules) and scabs may appear. In 

 one case under my direct observation there were four 

 successive crops of eruptions in four months (winter and 

 spring) on the teats and udder of the same cow. Crusts 

 from the third crop were mixed with dilute glycerine and 

 a calf was inoculated, by vaccination, producing an ulcer 

 with a scab or crust without apparently passing through 

 vesicular and pustular stages. Had I used the crusts 

 from the first crop I am confident true cow pox would 

 have been produced in the calf. Moreover, the calf inocu- 

 lated had been getting the milk from this cow (not 

 sucking) and may have become immune before being in- 

 oculated. 



