115
It will be seen from the above table that the ratio of the spleen to body weight increased, from a
minimum in the absent cases, in regular gradation, according to the number of hæmatozoa present in
the circulation of the rats.
The percentage increase in weight of the spleen in males and females under 60 grammes with the
hæmatozoon in their blood was 60 per cent, while in those over 60 grammes it was 73 per cent., above
the average weight of the spleen in rats, whose circulation was free from the organism.
About 60 per cent. of young rats from two to four months old, weighing up to 60 grammes, have
the hæmatozoon present in their circulation, and usually in large numbers.
The hæmatozoon of the rat appears and disappears from the circulation at irregular intervals, thus
producing paroxysms and intermissions, as is the case with the Surra Trypanosoma in equines, bovines
and other animals.
TABLE XXXIV.
Showing the number of Hæmatozoa, red and white Corpuscles, in one cubic millimetre of the blood of
Rats (Mus decumanus) together with their body weight and that of the principal organs and their
respective ratios.
I.
Serial
Number.
1
2
3
4
5
6
7
II.
Number in
Case Book.
1,406
1,140
1,104
1,402
1,156
1,171
1.417
III.
No. of
organisms.
(Abbrevia-
tions).
N.
V.N.
V.N.
V.N.
T.
T.
T.
IV.
Hæmatozoa
in blood
1 c. mm.
6,233
9,400
11,200
15,000
51,200
268,400
292,000
V.
Number of
red corpuscles
in 1 c. mm.
of blood.
6,350,000
6,320,000
6,970,000
7,550,000
4,850,000
5,450,000
6,060,000
VI.
Number of
white cor-
puscles in
1 c. mm.
4,400
2,600
8,600
5,200
11,000
6,000
19,000
VII.
Ratio white
corpuscles
to red.
1: 1,443
1 : 2,431
1 : 810
1 : 1,452
1 : 441
1: 915
1: 319
VIII.
Ratio of
hæmatozoa
to red
corpuscles.
1: 1,016
1:
672
1:
522
1:
503
1:
95
1:
20
1:
21
IX.
Body
weight of
rat.
Grammes
85.0
28.0
51.0
58.0
58.0
28.0
42.0
X.
Spleen
weight.
Grammes
1.70
0.05
0.25
0.25
1.45
0.29
0.71
XI.
Ratio of
Spleen
weight to
Body weight.
1 : 50
1 : 560
1 : 204
1 : 232
1 : 40
1 : 96
1 : 59
Microscopical examination of saliva proved the absence of the Trypanosoma, when the hæmatozoon
was swarming in the blood at the same time. Immediately, however, a slight wound of the mucous
membrane of the mouth was made, the organisms were discovered in varying numbers according to the
amount of blood mixed with the saliva.
The hæmatozoon was always found absent from the urine of rats, although swarming in the circula-
tion at the time of collection.
It has been observed in a considerable number of cases that although the hæmatozoon may be
present in vast numbers in the blood of pregnant rats, in no case has the organism been discovered in
the circulation of the fœtus. Of 2,154 rats examined, 1,070 were males and 1,084 females. Seventy-
seven females were pregnant, the hæmatozoon being present in the blood of 19, and absent from it in
58 ; or a percentage of 32.75 as against 67.25
Nematode worms, varying in number and dimensions—1 to 5 or 6 inches in length—were found in
the stomachs of rats, in which the hæmatozoon was either present, or absent. In some instances it was
fully distended by the number of parasites present, and little room could have been available for food.
In a total of 203 examined for parasites in 1893, nematodes were found in the stomachs of 40 or 19.75
per cent. Again, in 2,154 examined in 1894-95, nematodes were found in 23.58 per cent. It is of
interest to note that during the rainy season—June to November—the percentage was 16.27, whilst during
the months December to May it rose to 29.36 per cent. The percentage varied during the twelve
months from 7.25 in July to 37.50 in April. Therefore the nematodes and the Trypanosoma were not
at their maxima at the same time. This is accounted for by the fact that during the heavy rains the
ground and sewers are washed and flushed daily and the rats do not obtain as food filthy material, which
is seen so frequently during the hot season.
The hæmatozoon has never been found in the blood of the musk rat (Sorex cœrulescens) and mice
(Mus spicatus) although a large number have been examined.
Up to the year 1890, all inoculation experiments with the soiled blood of rats had proved negative
in their results; the animals employed being rats (Mus decumanus), dogs, cats, horses (6) and monkeys.
In the case of one monkey the result was doubtful, for Vandyke Carter states that " on microscopical
examination of the animal's blood, taken from a digit 18 and 24 hours after inoculation, two hæmatozoa
and one hæmatozoon were respectively observed. It did not, however, seem quite certain that a repro-
duction of the rat's organism had taken place in the circulation of the monkey; but possibly this was so
to a very limited extent."
Proof, then, was wanting as to whether the Trypanosoma of the rat was capable of producing Surra
in horses and other animals. For the purpose of deciding the above question two series of experiments
were instituted : (i) Inoculation of animals with the soiled blood of the rat (Mus decumanus), (ii) the
gastric ingestion of rat's excrement.