A Rapid Gravimetric Method of Standardising Vaccines

1. A method is described of rapidly evaporating to dryness bacterial emulsions contained in tarred flasks and from the increase of weight determining the strength of the emulsion.The same apparatus can be used for a variety of purposes, e.g. drying serum, estimating solids in water, milk etc.2. A very rapid method of drying bacteria smeared on a tarred piece of platinum foil, and from the dried residue preparing a vaccine is described.3. A correlation between the number and weight of bacteria in vaccines made from agar cultures of the B. typhosus, B. coli, B. pyocyaneus, Meningococcus (Weichselbaum), Pseudo-Gonococcus, Micrococcus melitensis, B. pneumoniae Friedlander, Staphylococcus aureus and Streptococcus has been established.4. The advantages of the gravimetric method are:(a) That with a sensitive balance constant results are obtained.(b) It is more rapid, and involves no strain ou the eyes.(c) It can be applied to cultures of all bacteria growing on solid media, whether these form uniform emulsions or not, e.g. vaccines of Streptococci, Micrococcus catarrhalis, Diphtheroid organisms, B. tuberculosis, Streptothrices can be accurately standardised. Even small clumps in the vaccine considerably vitiate the results in Wright's method. The chief precaution to take in the gravimetric method is to remove the growth carefully, without breaking the surface of the medium and avoiding the condensation water.(d) It brings into line the dosage of bacterio-proteins with that of other medical remedies.