CONTROL OF VIRUS DISEASES 85 
immune to measles it was suggested that the gamma-globulin fraction 
of the processed human blood might be used as a means of controlling 
measles since it was sure to be rich in antibodies to the disease. In 
Boston, U.S.A., a number of experiments were carried out to test this 
possibility with very interesting results. It was found that if 7 c.c. 
of the gamma-globulin rich fraction of processed blood was injected 
per pound of body weight, the individuals were completely protected. 
A quarter of this amount resulted in a very mild disease. 
In New York City another experiment was carried out on 814 
exposed individuals; 2c.c. of gamma-globulin was administered 
uniformly to patients between six months and six years of age. Sixty- 
five individuals in a control group received no gamma-globulin. 
The results of this test were interesting: of the 814 patients treated 
none developed regular measles, 2 per cent had a moderate attack, 
19 per cent had a mild form of the disease, and 79 per cent remained 
healthy. Of the sixty-five patients not treated, 48 per cent developed 
regular measles, 18 per cent moderate measles, 17 per cent mild measles, 
and only 17 per cent remained healthy. 
It should perhaps be emphasized that where there is complete 
prevention of the disease, there is no subsequent protection, but 
modification to a mild attack confers long, if not life-long, immunity. 
Since the serum of a convalescent, recovered, or artificially immu- 
nized animal contains antibodies which are capable of neutralizing 
the virus, it is possible to prepare serum-virus mixtures which are 
virtually non-infective. Such mixtures have been used to some 
extent against cattle plague and dog-distemper, the procedure usually 
being to inoculate the virus on one side of the animal, followed by an 
inoculation a little later on the other side with the immune serum. 
Much greater success, however, has been obtained in immunizing 
dogs against distemper by a combination of active and inactivated 
virus and this success was due to the pioneer work of Dunkin and 
Laidlaw. The virus, inactivated by means of formaldehyde, is injected 
first, and this initiates a low-grade resistance which allows the later 
inoculation of active virus. By this means a solid immunity is built up. 
In an experiment involving 650 hounds from twenty-three packs 
which had certainly been exposed to infection, the incidence of the 
disease was only 1-4 per cent and the death-rate only 0:3 per cent. 
Of a number of young hounds which were not inoculated almost all 
contracted the disease and half of them died. 
Slaughter. In order to prevent the spread of a very infectious virus 
