were at once lowered while the lymph was fully saturated. Liquid chloroform, coming in contact with the lymph, tends to kill the vaccine virus. The lowering of the temperature to 10° C. has for its object the prevention of injury to the virus by the action of glycerine at warm air temperature, in fact, all through, from the collection of the pulp until the lymph is finally sent to the post, every effort is made to keep the lymph as cool as possible, so as to retain the potency unimpaired by the effect of temperatures above freezing.
The great advantage of this method of removing the extraneous micro-organisms from lymph are obvious. The method, the details of which must be carried out with great care, has proved, after years of trial, perfectly safe, and, if the safeguards which have been described are attended to, no injury results to the vaccine virus. Lymph, by this method, can be rapidly and cheaply freed from extraneous germs, so that a pure product can be in the hands of vaccinators within three weeks from the date of collection. The results of vaccination on children, with chloroformed vaccine, are very satisfactory. Inflammation is reduced to a minimum, and, on the seventh day after vaccination, firm regular vesicles are obtained with a marked absence of inflammation in the surrounding tissues, the latter condition being the rule before the introduction of a germ-free lymph. An interesting experiment, with results bearing on the heat-resisting qualities of our chloroformed lymph, compared with lymph prepared by a number of other methods is worth putting on record at this point.
Three calves, showing vesiculation of fairly good quality, were selected and the pulp collected from each separately. These three pulps were each divided as follows:—
Two grammes labelled A, 2 grammes B, 2 grammes C and the remainder labelled D.
A was emulsified with four times its weight of normal saline containing 1 per cent phenol.
B was emulsified with four times its weight of normal saline containing 5 per cent phenol.
C was emulsified with four times its weight of normal saline solution.
D was emulsified with four times its weight of 50 per cent glycerine and water.
After emulsification 10 c.c. of D was taken and labelled D. The remainder was treated with chloroform vapour for 30 minutes and the
