5i4 
THOMPSON YATES LABORATORIES REPORT 
With regard to cultivating the small fine bacillus, our attempts were practically 
a failure. We used to cut out several of the mesenteric glands by means of the 
thermocautery and introduce them into the broth tubes by means of recently-heated 
forceps. In two cases we got a growth (in one case pure and in another case with 
another bacillus) in this manner ; the tubes were placed in hydrogen with pyrogallol 
and alkali. In the former case there was no apparent change in appearance, but on 
breaking up the gland large numbers of apparently growing ' small ' bacillus was 
found. In another case a mixed culture of Staphylococci and the small bacillus was 
obtained; subcultures in these cases failed to give any growth of the small organism. 
It is, perhaps, noteworthy that in a large proportion of these whole mesenteric gland 
cultures no ordinary faecal, etc., bacteria grew, though from the large size of the 
pieces, it might have been anticipated, that accidental contamination would have 
occurred, or that Sanarelli's bacillus would have appeared. It appeared desirable 
to search for a medium which would be favourable for the growth of the organism, 
and the last thing done before being taken ill was to make several brews of tissue 
from the last autopsy and also to prepare milk tubes. Upon returning to work 
these were full of moulds and could not be utilised at the last two autopsies I was able 
to obtain. It seemed then that a peculiar small fine bacillus was to be found in the 
organs of yellow fever cases, in the contents of the gut, in local spots presumably 
gnat bites on the skin, and in the stomachs and salivary sac (or oesophageal diverti- 
cula) of many of the gnats examined. Piecing this altogether, it suggested that the 
fever consisted in a gnat-borne and introduced infection, and that the small bacillus 
was the active agent. It may be noted that Finlay in his original mosquito theory 
looked to the inoculation of a bacterial parasite (a tetracoccus) by means of his 
mosquito. 
As a means of seeing whether a recognizable bacillus could be traced in the 
mosquito, a number of preparations of the stomachs and salivary (or accessory) sacs 
were made from mosquitoes which were caught at the leprosy asylum at Para inside 
the cottages of the lepers; some of these had obviously been feeding upon the serous 
subcutaneous exudation rather than actual blood. These specimens were made just 
before coming away, and were not stained for the leprosy bacilli ; now, unfortunately, 
they have become mislaid. It may be added that by the notes made of the appearances 
in the fresh state of the organs of these mosquitoes they were all devoid of the small 
bacilli found in other places. 
Soon after we had found the small bacilli in the brown night-biting gnat, 
C. fatigans, we received the first report of Major Reed's Commission, in which the 
day-biting S. fasciata was incriminated; the proof then was slight, and we thought 
that possibly their successful cases were due to the accidental bite of a night mosquito 
like ours. That the S. fasciata can convey the disease has since been proved. It 
seemed probable that if a bacterial parasite was concerned, and that subcutaneous 
