Assertion: vaccine | /r/HasProperty | produced on the skin of calves
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Source sentences:
text: Until the end of the 19th century, vaccination was performed either directly with vaccine produced on the skin of calves or, particularly in England, with vaccine obtained from the calf but then maintained by arm-to-arm transfer; initially in both cases vaccine could be dried on ivory points for short term storage or transport but increasing use was made of glass capillary tubes for this purpose towards the end of the century.