234 The Vaccine InstitiUe, Belgaunt.
reduce the extraneous germs sufficiently, to permit of issue. Certain lymphs purify quickly, while others are most resistant, and many months are often necessary before the germs are got rid of. In the meantime, the potency of the lymph has been endangered by prolonged storage, and such lymphs must be tried, to test their activity, before they can be issued with safety. Such uncertainty is very unsatisfactory and repeated bacteriological tests are required, entailing labour and expense. I am, therefore, strongly in favour of the method I have described for freeing vaccine lymph from extraneous micro-organisms and I can strongly recommend it to workers in the same field.
Storing, Tubing and Despatch.
After the lymph has passed through the chloroform process, office copies of each lymph number are taken in small 2 c.c. glass tubes, each corked with a sterile cork and dipped in melted paraffin. The rest of the lymph is filled into test tubes, corked securely and paraffined, leaving as little air between the lymph and the cork as possible. These separate lymph numbers are placed in wire baskets and kept in cold-storage with their corresponding office copies. When convenient, the office copies are taken out and agar plates are poured from each. Two loopfuls of lymph, weighing 10 milligrammes, are taken from each lymph number and mixed in a tube of melted agar culture medium at 42° C, well shaken up and poured into petri dishes. The plates are incubated at 37 °C. and colonies are counted after four days. Those plates showing 15 or less colonies are marked as passed for issue and entered in the despatch register accordingly. When more than 15 colonies are found, the lymph is stored for another week and again plates are poured from it. When colonies are reduced sufficiently, the lymph is passed for issue. It is rarely necessary to store lymph longer than a few weeks, as the large majority are ound pure enough at the first pouring to be passed.
Filling.
Lymph numbers are selected from the despatch register and the tubes taken from store and carefully decanted into a filling funnel. This is a glass funnel with a cover; a piece of rubber tube is attached, which has a spring clip and glass nozzle. The glass funnel containing the lymph is put into an outer copper container (A), mounted on a tripod stand (B) and surrounded by crushed ice and the cover fixed. The rubber tube, with clip attached, projects from the bottom of the copper container and the Assistant, who has charge of the filling, is provided with a copper box (C)
