216 SECTIONAL ADDRESSES. 
be well over 100. At least it may be said that, if M. Fourneau has not 
identified Bayer ‘ 205,’ he has discovered another compound having very 
similar, and probably as valuable, properties. 
NaSO, NH—co’ “CHy.) CHy-< Sco— NH  §0,Na 
font 2 NH 2 a 
| | 
NaSO CO CO SO,Na 
: inrea vas ee = 
SO,Na | | | | NaSO, 
NH—CO—NH\ 
vA Ww! 
Fourneau’s ‘309’ (possibly identical with Bayer ‘ 205’). 
The most remarkable property of ‘205’ is the long persistence of its 
effect. A dose injected into a mouse, a rabbit, or a rat will not only free 
the animal, if already infected, from trypanosomes in a few days, but will 
also render it resistant to such infection for a period of weeks or even 
months. During that period its serum, or extracts from certain of its 
organs, exhibit a curative action if injected into another animal infected 
with trypanosomes. 
Though there seems no reason to doubt that this substance has cured 
a number of cases of African sleeping-sickness in man, even some in which 
the disease was well advanced and in which all previously known remedies 
had failed, the mode of its action still presents a number of attractive 
obscurities. Like many other remedies which are experimentally efficient 
when injected into the infected animal, it has little or no obvious action 
when directly applied to trypanosomes in vitro. The paradox is, perhaps, 
less than usually significant in this case, since the action in the animal is 
delayed, a period of a few days elapsing before the trypanosomes begin to 
disappear from the blood. We might suppose that the action is too slow 
to be recognised during the period of survival of the parasites outside the 
body, or that it affects not the individual vitality of the trypanosomes, 
but their power of reproducing themselves. The latter idea is supported, 
as in other cases, by the fact that trypanosomes treated with the drug 
in vitro, or taken from an injected animal before the curative effect has 
become manifest, fail to infect another animal. It is contradicted, how- 
ever, by the observation that the trypanosomes, just before the curative 
action begins, show not a depression, but a stimulation of reproductive 
activity, division forms becoming abnormally common. Is it that during 
or immediately after division the parasites become specially liable to the 
action of the drug? It may be so; but one thing seems perfectly clear, 
namely, that the action is a very complex one, involving the co-operation, 
in some way, of the host. For here again it is found that the curative 
action, on infections by the same strain of trypanosomes, varies enormously 
with the species infected, a mouse being cured with ease, an ox or a horse 
with difficulty or not at all. A curious fact is that the rapidly progressive 
and fatal infections produced in mice by certain pathogenic trypanosomes 
are easily and certainly cured, while the apparently harmless natural 
infection, seen in many wild rats, by 7’. lewisi is not aftected at all. Then 
