A. Balfour 
287 
to them, was perfectly harmless, existing in them only as a saprophyte. It 
was not possible to find any such organism and in any case it was not feasible 
to employ wild rats for experimental purposes. Hence, as in the previous 
experiments, recourse was had to laboratory animals. 
It was considered best to make a start with Micrococcus catarrhalis as this 
organism affects mucous membranes, is very unlikely to be transmitted from 
rats to man and, even if so transmitted, is so mildly pathogenic to human 
beings and in any case so common in their nasal passages that any fresh source 
of infection might, it was felt, for practical purposes be disregarded. 
Accordingly a strain of M. catarrhalis (Gordon) was obtained from the 
National Collection of Type Cultures, Lister Institute, and cultures of it were 
used for the purpose of smearing the vaginas of tame rats. 
In the first instance the vagina of a tame rat was smeared with a 24 hours 
culture of this organism. This rat was put with a male a few days later. She did 
not become pregnant but this may have been due to the experiment being 
performed at a time which was not the normal breeding season. 
In the second case in which this organism was used a 24 hours culture 
was mixed with one of Staphylococcus albus which had been recently isolated 
from a case of gleet, and a heavy growth of these organisms was smeared on 
the walls of the vagina of one white rat which was afterwards put with a 
male. The former rat had a healthy litter 27 days after the inoculation. The 
mixed culture was used to see if symbiosis might play any part in patho¬ 
genicity. 
My attention having been directed to the work of Teacher and Burton 
on infective abortion in guinea-pigs, I wrote to Dr Teacher and he very 
kindly supplied me with two strains of the diphtheroid bacillus which he and 
his co-worker had shown to be the cause of the second epizootic which they 
reported. The first was due to streptococci, of which pure cultures had not 
been obtained, so it was not possible to employ these organisms in our investiga¬ 
tion. 
Although it appeared advisable to test the diphtheroid bacillus above- 
mentioned the outlook regarding its possible value was not very promising. 
Teacher and Burton were unable to bring about abortion by the introduction 
of cultures into the vagina and, as a result of their experiments, concluded 
that in all probability the natural and only route of infection is through the 
blood stream. They proved that the bacilli have a definite seat of election in 
the cavity of the yolk-sac. 
Sub-cultures were prepared from both the strains supplied by Dr Teacher 
and 24 hours growths were used for the inoculations. 
The vagina of a white rat was smeared with a mixed culture and it was 
placed with a male. 
The female died 2£ months later without becoming pregnant, the cause 
of death being abscess of the lung. The failure to conceive was not conclusive 
as the experiment was not conducted during the normal breeding season. 
19—2 
