ROB) 5 Schiiffner: Pseudotyphoid Fever in Deli 847 
and so small as to be scarcely visible to the naked eye. These 
acarines have been examined by Professor Nuttall, who found 
them to be of two kinds. One is the larval form of a Trombidium 
and resembles, therefore, the kedani mite. The other one, with 
the long legs, is the larval form of a Cheyletus. It has not 
been possible to determine the species in either case, as the 
adults are unknown. . 
The larval Trombidium of Deli differs from the Japanese form 
as figured by Tanaka in the structure of the body and of the 
mouth parts; the measurements correspond to those of the small 
form of the kedani mite (0.15 millimeter broad and 0.25 milli- 
meter long). The Deli mite is thick-skinned, not easy to crush, 
and its bite causes a violent itching after about fifteen minutes, 
while the bite of the Japanese variety may remain unnoticed 
until several days have. elapsed. 
In Deli we consider these acarines as suspect only, lacking 
direct proof of their association with the disease; their exist- 
ence in large numbers in the dangerous areas and the analo- 
gies which the disease presents with kedani fever would appear 
to justify this suspicion. Some of my patients had been bitten 
by a larger acarine, which I believe may be the nymph of a 
species of Hyalomma and which I have often observed to 
attack man. 
It can be affirmed with certainty that the Deli disease is 
transmitted to man by the bite of an arthropod and that it is 
not directly contagious. Moreover it is probable that there is 
a reservoir of the virus in another host as in the case of the 
field mouse of Japan. The development of the disease among 
recent immigrants in areas previously uninhabited proves this 
to be the case, unless one accepts the possibility that the virus 
may remain alive for a long time in man. 
SYMPTOMATOLOGY OF PSEUDOTYPHOID FEVER OF DELI 
THE DERMAL NECROSIS 
In 39 per cent of cases the original point of infection is dis- 
coverable; in Kuropeans, in all cases. It is much easier to rec- 
ognize the ulcer, often very small and after a time not very 
characteristic, on the healthy skin of a European than it is on 
that of the native, who is frequently a sufferer from other skin 
affections. It is for this reason that for a long time I overlooked 
the connection between the disease and the ulcer. 
In the earliest stage that I was able to observe, the lesion 
showed itself as a flat vesicle, 3 to 4 millimeters in diameter, 
