R. W. Fisher. 233
it may be stated, however, that a very great increase of germs, as shown on agar plates, occurred in the case of the saline-diluted lymph, while in 1 per cent phenol, and the glycerinated lymphs, the organisms were much reduced after seven days' storage at 37° C. Evidently, the growth of these germs is very injurious to the virus, and, if lymph is not prepared containing an active germicide, such as phenol or glycerine, the virus will suffer when the temperature of storage is above freezing point. In Noguchi's experiments, already referred to, he worked with a germ-free lymph obtained by his intratesticular method. Such diluents, as saUne distilled water and Ringer's solution, did not prevent the continued vitality of his virus at blood-heat; so it is evident, that the injurious factor is the growth of extraneous organisms, which are always present in lymph prepared from the skin. This would account, also, for the rapid deterioration, which has been shown to occur in the case of lanolinated lymph; as the lanoline exerts no germicidal action and the extraneous germs are free to grow and, by the action of their toxins, in Cure the virus. These experiments are all in favour of glycerine as a diluent for vaccine lymph, as neither the glycerinated nor glycerinated and chloroformed lymphs showed the deterioration which was so marked in the phenolated and saline diluted lymphs. The vesiculation, in the case of the chloroformed lymph, was rather better than that given by the glycerinated lymph, while the vitality was very similar in both. The chloroformed lymph was rendered practically free from extraneous germs, the agar plates only showing 10 colonies, while in the case of the glycerinated sample, many organisms were present, but became rapidly reduced at blood-heat and room-temperature. In cold-store, the glycerinated lymph showed a slow but steady reduction of extraneous organisms 12 colonies being present in 10 milligrammes after 28 days' storage. The experiment, therefore, confirms the experience gained in the districts with chloroformed glycerinated lymph and ratifies the opinion, previously-formed, that glycerinated lymph, carefully treated with chloroform vapour, has very satisfactory heat-resisting qualities and can be depended upon to retain its potency, at blood-heat, for two weeks and at room-temperature for four weeks.
Purification by the chloroform method is under complete control, as the bacteriological test is a sure guide to the amount of choroform necessary to reduce the organisms always present in crude lymph. When dependence is placed on glycerine alone to purify the lymph, it is impossible to determine how long it will require for the glycerine to
