PROPHYLAXIS AGAINST EQUINE SURRA                       287

The foregoing table shows that while a dose of 7.5 grammes of " Bayer 205 "
per 1,000 lb. body weight protected up to 22 days, a dose of 10 grammes failed to
confer protection for 2 months.

Kasai and Akazawa [1927], in Formosa, record the results of a series of
experiments carried out by them upon the prophylactic action of "Bayer 205"
against a species of trypanosome which they regard as being " in all probability
identical with T. evansi", the disease caused by it affecting water-buffaloes,
zebras, and dogs in that country. In mice, 0.005 gramme of the drug conferred
protection from experimental infection for 5 months. With 0.00003 gramme,
" some of the injected mice were completely protected and others had death delayed
for several days", whereas 0.00001 gramme had almost no prophylactic action,
so that 0.00003 gramme proved to be the minimum dose exercising any protective
power. In calves, subcutaneous injection of 1 gramme per 100 kilo. body weight
protected for a period of 4 months, whereas in horses a dose of 1 gramme per 100
kilo. body weight was not protective " even one month after introduction",
although the duration of the disease was prolonged. Doses of 2 grammes per 100
kilo. body weight, however, protected for 3½ months. ( Cf. Bubberman, infra,)
The authors would seem to regard the special virtue of " Bayer 205 " as consisting
in its prophylactic, rather than in its therapeutic properties, and they even consider
the discovery of this drug " as an epoch-making event to open the field of ' chemo-
prophylaxy' as salvarsan to chemotherapy ".

Kleine [1924], however, records having obtained very unsatisfactory results in
regard to the prophylactic action of " Bayer 205", against experimental
infection with Trypanosoma theileri, T. brucei, T. congolense and trypanosomes
of the vivax group, for even a dose of 10 grammes of the drug for a
bullock of about 5 cwt. failed to prevent infection with these trypanosomes.
Certain other workers, too, have recorded their failure to use the drug successfully
against T. congolense or T. vivax infection. Thus, Van Saceghem [1925] succeeded
in setting up infection with these parasites in all of a group of three bovines that
had previously received 5 grammes of " Bayer 205 " per kilo. bodyweight, the
intervals ranging from a fortnight down to simultaneous injection of the drug.

      PROPHYLACTIC ACTION OF "BAYER 205" AGAINST NATURAL TRYPANO-

                                              SOMIASIS.

A perusal of the available literature shows that there are remarkably few
observations on record in regard to the prophylactic action of " Bayer 205"
against natural trypanosomiasis of animals. This doubtless, to a large extent, to
be ascribed to the fact that it is barely ten years since the drug was introduced