Calf lymph was the name given to a type of smallpox vaccine used in the 19th century, and which was still manufactured up to the 1970s.
History
Calf lymph was known as early as 1805 in Italy, but it was the Lyon Medical Conference of 1864 which made the technique known to the wider world. In 1898 calf lymph became the standard method of vaccination for smallpox in the United Kingdom, when arm to arm vaccination was eventually banned (due to complications such as the simultaneous transmission of syphilis).
References
Calf lymph Wikipedia(Text) CC BY-SA