222 SECTIONAL ADDRESSES. 
the truly parasitic Entameba histolytica, which cannot live without invading 
the tissues, can be checked in this invasion and eliminated from the body 
by administering emetine, while other Entamcebe, which live on fecal 
debris, remain unharmed. Whether the tissues are so altered that the 
amcebe cannot invade them, or the amcebe, without being directly killed, 
are so weakened in virulence that they cannot invade the tissue and obtain 
their food, but succumb in face of the normal resisting powers of the host, 
are possibilities on which we can only speculate, and no method of bringing 
them to the test of experiment has yet been found. 
The work of Morgenroth and his co-workers, extending now over more 
than a decade, has again led them to emphasise, in connection with the 
curative action of substances which they have examined, a fixation to the 
cells and tissues of the host, a definitely organotropic property, as an 
important factor in the effect. Two examples may be mentioned. 
V. Quinine and Malaria. 
One of the earliest of chemotherapeutic discoveries, that of the cure of 
malaria by quinine, had never been satisfactorily explained. There was no 
evidence establishing even a probability that quinine, in such concentrations 
as can be tolerated in the blood of the living subject, would directly kill the 
malarial plasmodia, especially if these were partly screened from its action 
by their position in the interior of the red corpuscles. Morgenroth, from 
the results of his determinations by biological methods of the distribution 
of quinine in blood, is led to the conception of quinine as acting on malaria, 
in virtue of its fixation by the red corpuscles, either killing the trophozoites 
in their interior, or blocking the entry into them of the merozoites of the 
asexual cycle. On this latter supposition, it will be seen that quinine would 
act, not by killing the malarial parasites, but by rendering the blood un- 
fitted for their multiplication. They are supposed to fall a prey to the 
natural defensive substances in the plasma, because a film of quinine denies 
them access to the red corpuscles, in the interior of which they could 
continue their development in safety. There are discrepancies between 
Morgenroth’s determinations of the distribution of quinine in favour of 
the red corpuscles, and those obtained by direct chemical means, which 
would still need to be reconciled before either theory of the curative process 
in malaria could be fully accepted. Meanwhile, these suggestions are of 
interest as another example of the need found, more and more, by workers 
in this field to regard an organotropic property of a drug not as detri- 
mental to its curative action but as an essential factor in the chemo- 
therapeutic process. 
VI. Remedies for Bacterial Infections. 
This same property, of fixing themselves to the red blood corpuscles or 
to the connective tissue, has been observed by Morgenroth and his co- 
workers with the higher homologues of quinine, ethylhydrocupreine 
(* optochin *) and octylhydrocupreine (‘ vuzin’), and with the dyes of the 
acridine series, with which they have obtained promising results in the 
treatment of bacterial infections. In the treatment of pneumococcus 
infections by optochin several factors, other than those of immediately 
