3

(also of mice), gave negative results. Vandyke Carter's inoculation experiments
included the subcutaneous injection into healthy animals of tainted blood of the
rat, the animals so employed being rats, dogs, cats, horses (6), and monkeys.
On microscopical examination of the last-named anunalVblood, taken from a
digit 18 and 24 hours after inoculation, two hæniatozoa and one hæmatozoon
were respectively observed. It did not however seem quite certain that a
reproduction of the rat's organism had taken place in the circulation of the
monkey; but possibly this was so to a very limited extent. These inoculation
experiments therefore all proved negative in their results, except in the doubtful
case of the monkey.

B.—Experimental investigations re Hæmatozoon in Rats and
Bandicoots at the I. B. Laboratory.

From November 1890 to May 1892, the blood of 349 rats was examined
microscopically, and the hæmatozoon was found present in 106, and absent in
243, giving a percentage of 30.37 present to 69.63 absent. Again, from June
1892 to July 1894, the blood of 758 rats has similarly been examined, but with
the elucidation of more details, and with the following results :

                                                 TABLE I.

              Showing the Rats (M. d.) examined from June 1892 to July 1894, and the relative
                                                  number of organisms in their circulation.

                                          TABLE II.

              Showing total number of Rats (M. d.) examined during the years 1890—1894, with,
                                                  number of hæmatozoa present and absent.

        2.    Dividing the (Bombay) year into two periods,

              (i) Dry. and hot (January to May inclusive),
              (ii) Rainy and humid (June to December inclusive),
we find that during the period, November to June 1894,421, out of a total of
1,107 rats examined, contained the hæmatozoon in their circulation. It was
present in 31.53 per cent of the rats caught from January to May, and 40.31
per cent of those obtained from June to December, or during the rainy season.
Although in the hot season the hæmatozoon is present in the circulation of
these animals, the organisms are very few in number, while during the latter
period of the year they are far more numerous, the percentage of cases in which
the hematozoa are very numerous or swarming, being 24.00 in the dry season
and 52.61 in the, rainy season, or in a ratio of 1:2.19.

3.    There is a tendency in the hematozoon to disappear from the circulation
of some rats, when kept in captivity and supplied with clean food and water.

4.    About 60 per cent of young rats from 2 to 4 months old have the
hæmatozoon present in their circulation, and usually in large numbers.