NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
Surra.
33
PONY 258.
Aug. 7th
„
14th
„
14th
„
15th
„
16th
„
25th
„
27th
„
29th
„
31st
Sept.
2nd
„
4th
„
6th
„
8th
„
10th
„
14th
„
16th
... Inoculated with Surra ......
...
......
Tryps. appeared in blood
... 40 c.c. of 10% Atoxyl +2
„
.. ...
gms. of Orp.
... 40 c.c. of 10% Atoxyl+2 „
absent
gms. of Orp.
... 40 c.c. of 10% Atoxyl × 2
„
„
gms. of Orp.
.. 70 c.c. of 4%
Atoxyl „
reappeared
... 2 gms. of Orp.
„
absent
.. 100 c.c. of 4% Atoxyl
„
„
.. 1 gm. of Orp.
„
„
... 100 c.c. of 4% Atoxyl „ „
... 1 gm. of Orp.
„
„
... 100 c.c. of 4% Atoxyl
„
„
... 1 gm. of Orp.
„
„
.. 125 c c. of 4% Atoxyl
„
... 1 gm. of Orp.
„
„
... 100 c.c. of 4% Atoxyl
„
„
„
24th to 28th
...
„
reappeared
Sept. 28th
„
30th
Oct.
6th
„
8th
„
12th
Treatment changed.
... 50 c.c. of 1% Tartar
...
...
Emetic.
... 500 c.c. of Sodium Arsen-
absent
ite in drench.
... 500 c.c. of Sodium Arsen-
„
ite in drench.
...
......
Tryps. reappeared
... Destroyed.
Body weight.
in lbs.
535
549
...
549
545
515
520
521
520
525
525
525
525
...
...
...
530
525
525
513
...
PONY 265.
Aug. 7th
„
13th
„
14th
„
15th
„
16th
Sept. 3rd
„
3rd
„
5th
„
7th
„
9th
„ 11th
„
13th
„ 15th
„ 17th
„ 19th
„ 21st
... Inoculated with Surra
......
...
...
Tryps. appeared in blood
... 20 c.c. of 10% Atoxyl + 1 gm. of Orp. Tryps. present
... 20 c.c. of 10% Atoxyl + 1 gm. of Orp. „
absent
... 30 c.c. of 10% Atoxyl + 1 gm. of Orp. „
„
... ... „ reappeared
... 50 c.c. of 4% Atoxyl
... 0.5 gm of Orp.
„
absent
... 50 c.c. of 4% Atoxyl
„
„
... 1 gm. of Orp.
„
„
... 50 c.c. of 4% Atoxyl
„
„
... 1.5 gm. of Orp.
„
„
... 50 c.c. of 4% Atoxyl
„
„
... 1.5 gm. of Orp.
„
„
... 50 c.c. of 4% Atoxyl
„
„
... 1.5 gm. of
Orp.
„
„
Body weight
in lbs.
300
303
303
300
310
315
315
320
320
320
.
.
.
......
3
34
Surra.
Oct. 1st
„ 1st
„ 1st
„ 3rd
„ 5th
„ 8th
„ 10th
„ 12th
„ 14th
„ 16th
„ 18th
„
20th
„
25th
„
25th
„
26th
„
27th
„
29th
„
30th
Nov. 2nd
„
3rd
„ 4th
... Tryps. reappeared
...
Treatment changed.
... 50 c c. of 4% Atoxyl
„
present
.. 300 c. c. of Sodium Arsenite in drench. „
absent
... 50 c. c. of 4% Atoxyl
„
„
... 50 cc. of 4% Atoxyl
„
„
... 300 cc. of Sodium Arsenite in drench
„
„
... 40 c.c of 4% Atoxyl
„
„
... 300 c c. of Sodium Arsenite in drench
„
„
... 40 c.c. of 4% Atoxyl
„
„
... 300 c c. of Sodium Arsenite in drench
„
„
... 40 c.c. of 4% Atoxyl
„
„
...
...
„ reappeared
... Treatment changed
„
... 600 c.c. Sodium Arsenite in drench
„
present
... 2 gms. of Orp.
„
„
... 600 c.c. of Sodium Arsenite in drench
„
absent
... 2 gms of Orps.
„
„
... 700 c.c. of Sodium Arsenite in drench
„
„
... 50 c.c. of 4% Atoxyl
„
„
... 3 gms of Orp.
„
„
Body weight
in lbs.
......
......
345
354
354
359
355
350
348
336
339
340
350
344
344
345
350
347
347
Severe colic followed and the pony died on 7th November
1908.
PONY 282.
Sept. 11th
„
14th
„
21st
„
28th
„ 29th to 1st
Oct.
1st
„
3rd
„
5th
„
7th
„
9th
„ 10th
... 50 c.c. of 4% Atoxyl
......
.. 1 gm. of Orp. ......
... Inoculated with Surra
......
... ......
Tryps. appeared in blood
„
present
... 50 c.c. of 4% Atoxyl
„
„
... 2 gms. of Orp.
„
absent
... 50 c.c. of 4% Atoxyl
„
„
... 2 gms. of Orp.
„
„
... 50 c.c. of 4% Atoxyl
„
„
... Feeds slowly. Temp. elevated
Body weight
in lbs.
267
......
......
285
377
373
350
354
366
378
Severe colic followed and pony died on the 13th October
1908.
PONY 280.
Sept.
12th
... Inoculated with Surra
......
„
18th
...
......
Tryps. appeared in blood
„ 19th &
20th
......
„
present
„
20th
... 50 c.c. of 4% Atoxyl
„
„
Body weight
in lbs.
...
275
275
274
Surra.
35
Sept.
„
„
Oct.
„
„
22nd
24th
26th
1st
3rd
5th
... 1.5 gm. of Orp
... 50 c.c. of 4% Atoxyl
... 60 c.c. of 4% Atoxyl
... 50 c.c. of 4% Atoxyl
... 1.5 gm. of Orp.
... 50 c.c. of 4% Atoxyl
Tryps.
„
„
„
„
„
absent
„
„
„
„
„
Body weight
in lbs.
265
274
282
256
245
246
Severe colic followed and the pony died on 7th October
1908.
PONY 289.
Sept
Oct.
„
......
„
„
„
„
„
28th
5th
5th
7th
9th
11th
13th
15th
16th
... Inoculated with Surra
... ......
... 25 c.c. of 1% Tartar Eme-
tic (intrav.)
... 1 gm. of Orp.
... 25 c.c. of 1% Tartar Eme-
tic (intrav.)
... 1.5 gms. of Orp.
... 25 c.c. of 1% Tartar Eme-
tic (intrav.)
... 1.5 gms. of Orp.
.. Feeds slowly. Temp.
elevated.
Tryps.
„
„
„
„
„
„
......
appeared in blood
......
absent
„
„
„
„
„
Body weight
in lbs.
200
196
...
200
204
215
212
198
198
Severe colic followed and the pony died on 19th October
1908.
At the time of publication of this Memoir, June 1909, the
following ponies are still under daily observations :—Nos. 288,
292, 285, 283, 260, 263, 245, 247, 249 and 250.
No Trypanosomes have appeared in their blood. All the
animals remain in good condition.
Pony No. 245 and Horse No. 263 have been doing hard
work.
It will be noticed that the doses of orpiment used by
Laveran and Thiroux are much larger than the amounts which
our animals tolerated. They administered up to 30 gms. of
orpiment. The maximum amount which the heaviest horse
treated by us could stand was 3 gms.
This is explained by the fact that the French Authors
used "Orpiment Precipite," while we employed commercial
samples of the drug, and of this there are two samples ; one
36
Surra.
of bright yellow color and of heavier specific gravity than
the second which is of a brownish tinge.
Dr. Hankin kindly analysed these specimens and informed
me that the first contains 72 % of a substance soluble in
dilute hydrochloric acid. This soluble substance consisted
chiefly or entirely of white arsenic.
No. 2 contains 2.6 % of substance soluble in dilute hydro-
chloric acid.
In our experiments we found that the second sample of
orpiment was of no use in the treatment of Surra and in
small doses caused colic.
PART II.
IMMUNISATION AGAINST CHARBON
SYMPTOMATIQUE BY MEANS
OF A SINGLE VACCINE.
The well-known system of vaccination against Charbon
Symptomatique discovered by Arloing and Cornevin, has for
many years been practised with so much success that any fur-
ther attempts to improve on this method may appear from a
practical point of view unnecessary. The immunity established
by these vaccines is undoubtedly of a solid and durable nature.
Statistics go to prove that in Black Quarter districts the
mortality which ranged from 2 to 25% has by means of this
vaccination been reduced to 1%. It is also recorded that vac-
cinated animals were found to be protected the year following
that in which they were treated.
However, during recent years, this system of vaccination
has not met with the same approval as it at first received. The
main reason for this is that frequent accidents have occurred
after the use of the vaccines. The average mortality after vac-
cination is extremely small, being less than 1%, but this mor-
tality is not evenly distributed. For some unexplained reasons
a large number of deaths at times occur after the use of either
the first or the second vaccine.
In one instance, recorded in England, fifteen cattle were
inoculated with quarter evil vaccine and within the next three
days five of them died from inoculation quarter evil.
The same vaccine was used in forty-eight other cattle in
different herds without any accidents. In another case eight
animals were inoculated. On the third day after the use of
the second vaccine, two out of the eight, died with lesions at
the point of inoculation.
In Switzerland, in 1895, a mortality of 7.8 per 1,000 was ex-
perienced. The same vaccine used in France and Holland
gave a result of 0.72 per 1,000.
38
Charbon Symptomatique.
Many similar instances of a heavy rate of mortality after
the use of vaccines are on record and have induced a certain
amount of prejudice against the system.
JOURNAL OF
COMPARA-
TIVE PATHO-
LOGY AND
THERAPEU-
TICS, 1895.
There appears to be no satisfactory and accepted explana-
tion of these accidents after vaccination. In discussing the
mortality which occurred in Switzerland in 1895, Cornevin
brings forward evidence that the casualties were not due to
the use of vaccines of excessive virulence. He suggests a
special and temporary susceptibility on the part of the cattle
inoculated in this country. He states that a marked and
altogether peculiar sensibility of certain animals and certain
families of animals with reference to Black Quarter is not a
new fact, as it has been previously observed at various places.
It may be due to a gross condition of the animals or to the
association of certain non-pathogenic microbes.
OESTEREICH
MONATS FUR
THIER, 1895.
In a review of the accidents resulting from the practice
of Kitt's method of single vaccination it is concluded that
" accidents cannot be avoided either by the system of vaccina-
tion at one operation or by using two vaccines," as it is not
known what are the circumstances that determine a change
in the virulence of the inoculating material.
Some of the fatal cases occurred in weakly or diseased
animals or in animals which after the inoculation of the first
vaccine were immediately overdriven. It is also known that
death may be due to a special disposition of the animals; to
traumatic injuries inflicted at the time of inoculation or after-
wards ; to the injection of too large doses of the vaccine ; or
to decomposition of the vaccine caused by heat, chemicals or
other influences. Virulence of the vaccine is very variable
and depends on whether the muscular tissue has been taken
from an animal which has succumbed or from one that has
been slaughtered. Also on other conditions, as whether the
animal has been bled or not, how long it was ill, whether the
bacilli were numerous in the material from which the vaccine
was prepared and in the length of time in drying.
ANNALES DE
L' INSTITUT
PASTEUR,
1902, 1903,
1908.
Leclainche and Vallee who have devoted much time and
labour to the elucidation of this subject in their earlier publica-
tion of 1900, were inclined to the view that the impurities of
the muscle vaccine was a factor in the accidents after vaccina-
Charbon Symptomatique.
39
tion. To eliminate this they recommended the use of pure
vaccines prepared either from the heart blood immediately
after death or from culture of the virus. Further experience
proved that these pure vaccines, even when they are very
attenuated, are not free from risk and that the results are not
better than those obtained from the impure vaccines.
In their latest publication on this subject they express
their conviction, that the accidents are almost always due to
latent infection at the time of inoculation and state that " we
have been able to make a series of experimental and practical
observations which do not leave any doubt regarding the rôle
of latent infection in the production of accidents following
vaccination. " In consequence they advise a method of con-
ferring a passive immunity by means of a protective serum, to
be followed after a short interval by an attenuated virus.
MacFadyean, in reviewing this publication, expresses views
in opposition to the theory of " latent infection " and to the
sero-vaccination method of immunizing. He is of opinion
that the individual susceptibility is the explanation most in
accordance with observed facts.
In recent years other systems of single vaccination have
been largely advertised and practised with varying success.
In 1903, Thomas introduced a single method of vaccination.
This vaccine is termed " Blacklegines " and consists of a thread
saturated with vaccine which is introduced under the skin in
form of a seton.
Another preparation " Blacklegoids " is sold in the form
of pillules by Messrs. Parke Davis and Co. These are injected
subcutaneously by means of a special syringe. They have this
advantage that the method of operation is simple and rapid.
Partly for this reason their use has met with the general
approval of the officers engaged in combating infective diseases
in India, and they are said to be the form of vaccine most
applicable to the conditions of this country. For some years
the double vaccines have been prepared at the Muktesar Bac-
teriological Laboratory, but there has been little demand for
them.
The necessity of two operations at an interval of several
days, combined with the danger of contamination of the vaccine
40
Charbon Symptomatique.
during process of manipulation renders them little suitable
for use in India.
In every country the success of an anti-serum or vaccine
depends upon simplicity of operation, freedom from accidents
and period of immunity conferred. In India, the first two quali-
fications have to be considered somewhat at the expense of the
third. New methods are regarded with suspicion by the owners
of cattle, and it requires the utmost tact and diplomacy to
induce them to submit their animals for treatment.
To the Hindoo, the life of the cow, as a rule, ranks higher
than that of a human being. Consequently any measures of
treatment adopted for their benefit must, above all considera-
tions, be free from any risk of accidents.
The following experiments were carried out in order to
determine the method of vaccination safest and most easy
of application to the cattle of this country.
In all the following experiments the same virus was used.
This consisted of the dried muscle juice taken from a bull dead
of Black Quarter.
The dried powder was diluted in proportion of 0.2 grammes
in 5 c.c. of normal salt solution. Of this solution 1 c.c. was
determined to be a reliable lethal dose for all susceptible bovines.
Susceptibility of Indian Bovines to experimental Inoculation of
Black Quarter.
Effect of virus inoculated intramuscularly.
Class of Animal.
Plains Bull ...
Hill Bull ...
„ ...
„ ...
„ ...
„ ...
„ ...
Plains Buffalo ...
„ ...
„ ...
„ ...
„ ...
Guinea-pig ...
„ ...
Lab. No.
79
424
447
7542
7637
7541
7644
116
14
15
7
115
150
151
Age.
9
1½
1½
1¼
1½
4½
1
1
5
5
...
...
Quantity
of virus inocu-
lated.
1 c.c
,
,
,
„
„
„
„
„
0.5 c.c.
„
Result.
Died after 36 hours.
Lived.
Died after 28 hours.
Died after 5 days.
Died after 30 hours.
Died after 48 hours.
Died after 36 hours.
Lived.
Died after 56 hours.
Died after 36 hours.
Lived.
„
Died after 24 hours.
Died after 25 hours.
The above animals were used as Controls in the experi-
ments testing the vaccines.
Charbon Symptomatique.
41
The results show that young animals possess a very high
degree of susceptibility to experimental intramuscular inocula-
tion of this amount of virus and that death takes place in a very
short interval after the inoculation.
It was found that the addition of Lactic acid to the virus
was unnecessary and did not in any way increase the virulence.
Effect of virus inoculated subcutaneously with and without
Lactic acid.
Class of Animal.
Hill Bull. ...
„ ...
„ ...
„ ...
„ ...
Plains Buffalo ...
„ ...
„ ...
Hill Bull
„ ...
Lab. No.
360
454
520
519
496
6
16
30
9461
9243
age.
2
1
2½
2
1
1
1
1½
2
1
Quantity of virus
inoculated.
1 c. c. mixed with a
drop of Lac. acid.
„ ...
„ „ ...
„ „ ..
„ without Lac. acid.
„ „ ...
„ „ ...
„
in Lac. ac. ...
„
no Lac. ac. ...
„ „ ...
Result.
Died in 21 hours.
No reaction. Lived.
„
„
„
„
„
„
Died in 24 hours.
Died in 36 hours.
The susceptibility to the virus inoculated subcutaneously
is extremely slight compared to the mortality resulting from
the virus injected intramuscularly. In these operations great
care was taken that the needle did not enter the muscle.
All the animals which survived the inoculation were tested
with virus injected intramuscularly twenty-five days after the
first operation and all were found to have acquired an
immunity.
TESTING THE VALUE OF CERTAIN VACCINES.
The vaccines selected for this purpose were:—
(a) Blacklegoids, a single vaccine in pellet form pre-
pared by Messrs. Parke Davis and Co.
(b) A single vaccine prepared from the blood of a bull
taken before death from Black Quarter.
The blood was incubated for 48 hours, dried,
powdered and exposed to a moderate temperature
for several hours.
(c) A mixture in fixed proportions of a first and second
vaccine, prepared somewhat after the method
of Arloing and Cornevin.
42
Charbon Symptomatique.
(d) The first and second vaccine of Arloing and
Cornevin.
The latter three vaccines were prepared at this Laboratory.
Testing Blacklegoid (a).
No. of Bull.
7660
370
350
406
400
Age.
Years.
1
2
1¼
2
2
Quantity of
vaccine used
sabcutancously.
1 pillule
1 „
2 „
2 „
2 „
No. of days
tested after
vaccine.
8
14
14
25
25
Quantity of
virus inoculat-
ed
intramus-
cularly.
1 c. c.
„
„
„
„
Result.
Died in 24 hrs.
Lived.
Died.
Lived.
„
Testing single vaccine (b).
No. of Bull.
7690
7673
491
367
6983
Buf. 121
490
375
357
433
452
Age.
Years.
1½
1
2
2
1
...
2
1½
2
1
1
Quantity of
vaccine used
subcutaneonsly.
.005 gm.
„
„
„
„
„
„
0.5 gm.
„
„
„
No. of days
tested after
vaccine.
8
8
14
14
14
14
14
14
14
25
25
Quantity of
virus inoculated
intramuscu-
larly.
1 c.c.
„
„
„
„
„
„
„
„
„
„
Result.
Died.
„
Lived.
„
„
„
Died.
„
„
Lived.
„
In the above experiments with Blacklegoids and vaccine
(b), it will be observed that after the use of a single dose no
protection against the disease had been established eight days
after the inoculation, but that a solid immunity had been con-
ferred fourteen days after the operation.
Also, that when larger doses of the vaccine were used, the
period necessary for the acquirement of the immunity was con-
siderably lengthened. The animals, when tested with virus,
on the 14th day succumbed, but those tested twenty-five days
after receiving the vaccines showed no reaction to the virus.
It is evident from this that the immunity acquired by treat-
ment with vaccines does not set in before an interval of eight
to fourteen days when a small dose of vaccine is used and that
when larger doses are inoculated, a longer period is necessary
before protection is established.
Charbon Symptomatique.
43
Further, it appears that during this interval the animals
inoculated with vaccine are in a state of hyper-susceptibility
to the disease, as they succumb to a lethal dose of the virus
in a much shorter time than the controls do. Some of the bulls,
which died at this stage after receiving the virus, were dead in
less than twenty hours after the inoculation, without showing
any of the usual clinical symptoms of the disease. This nega-
tive phase which results after vaccination and which varies
in duration with the amount of vaccine used, is a very probable
explanation of many of the accidents which occur in the field.
Judging from the results of our experiments it is safe to
conclude that the cattle of India can resist large doses of a
strong vaccine injected either subcutaneously or intra-
muscularly even with the addition of Lactic acid.
A high percentage are also tolerant to the pure virus when
inoculated subcutaneously, though they are very highly
susceptible to the intramuscular inoculation of the virus.
Consequently there is little danger of accident resulting
from such causes as variation in the strength of the vaccine
or individual susceptibility among these cattle. When animals
which have been treated with vaccine are exposed to infection
during the period of hyper-susceptibility following the vaccin-
ation, there is undoubtedly a slight risk of accidents.
Testing of single vaccine (c).
No. of Bull.
417
420
488
311
351
364
410
414
Age.
Years.
3½
2½
3
2
1½
6
4
2
Quantity of
vaccine used
subcutaneously.
Gm.
.005
.005
.005
.005
.005
.005
.005
.005
No. of days
tested after
vaccine.
14
14
14
14
14
14
25
21
Quantity of
virus inoculated
intramuscularly.
c.c.
1
1
1
1
1
1
1
1
Result.
Died.
Lived.
„
„
„
„
„
„
Testing double vaccine (d).
No. of Bull.
369
353
Age.
Years.
2
2
Quantity of
vaccine used
subcutaneously.
1st vac.
Gm.
0.01
0.01
2nd vac.
Gm.
0.01
0.01
Interval of days
between 1st &
2nd vaccine.
10
10
Quantity of virus
inoculated intra-
muscularly, 25 days
after the inoculation
of 2nd vaccine.
c.c.
1
1
Result.
Lived.
„
44
Charbon Symptomatique.
COMPARATIVE TEST OF BLACKLEGOID, VACCINE (b) AND VACCINE
(c).
Ten bulls were inoculated with one Blacklegoid each, ten
with .005 gm. of single vaccine (b) and ten with .005 of mixed
vaccine (c). These bulls were tested on the 26th day after the
vaccination by the inoculation intramuscularly of 1 c.c. of a
solution (0.2 gm. in 5 c.c. normal salt solution) of virulent
muscle juice with the following result :—
BLACKLEGOIDS.
No. of Animal.
526 ...
...
517 ...
...
476 ... ...
8514 ... ...
892 ... ...
375 ... ...
7856 ... ...
6364 ... ...
482 ... ...
522 ... ...
321 ... ...
518 ... ...
480 ... ...
371 ... ...
7363 ... ...
438 ... ...
274 ... ...
524 ... ...
525 ... ...
8513 ... ...
7359 ... ...
273 ... ...
326 ... ...
376 ... ...
378 ... ...
383 ... ...
393 ... ...
8091 ... ...
8955 ... ...
7349 ... ...
Age.
Years.
4
4
5
1
2
4
2
6
1
5
Single vaccine (b.)
6
2
3½
5
7
5
5
1½
2
2
Mixed vaccine (c.)
7
5
4
2
3
4
2
2½
1
6
Result.
Lived.
„
„
„
„
„
„
Died after 36 hrs.
Died after 48 hrs.
Died after 48 hrs.
Lived.
„
„
„
„
„ Died after 48 hrs.
Died after 48 hrs.
Died after 3 days.
Lived.
Lived.
„
„
„
„
„
„
„
„
„
Comparison of the immunizing effect of Blacklegoids,
vaccine (c), unattenuated virus and the double vaccine against
a lethal dose of virus inoculated after an interval of seven weeks.
Charbon Symptomatique.
45
VACCINE (c).
No. of Ball.
9250 ... ...
9237 ... ...
9264 ... ...
9265 ... ...
Age.
Years.
1
1
1½
2
Quantity of vaccine
used subcuta-
neously.
.005 gm.
.005 „
Blacklegoids.
2 pillules.
2 „
Quantity of vaccine
inoculated intramus-
cularly.
1 c.c.
1 „
1 c.c.
1 „
Result.
Lived.
„
Lived.
„
UNATTENUATED VIRUS.
The virus used was the same as employed throughout
all the experiments and consisted of 0.2 gm. of muscle juice
dissolved in 5 c.c. physiological salt solution.
No. of Bull.
9249 ... ...
9322 ... ...
Age.
Years.
2
1¾
Quantity of virus
used subcutane-
ously.
1 c.c.
1 „
Quantity of virus
inoculated
intramuscularly.
1 c.c.
1 „
Result.
Lived.
„
DOUBLE VACCINES.
No. of Bull.
9238 ... ...
9244 ... ...
Age.
Years
1
2
QUANTITY OF VACCINE
USED SUBCUTANEUSLY.
1st vaccine.
0.01 gm.
0.01 „
2nd vaccine.
0.01 gm.
0.01 „
Interval of
days bet-
ween 1st
and 2nd
vaccine.
12
12
Quantity of
virus inocu-
lated intra-
muscularly.
1 c.c.
1 „
Result.
Lived.
„
With the exception of Bull No. 9249 (virus) which had a tem-
perature of 39.4°C. on the clay following the last inoculation
of virus, and Bull No. 9322 (virus), which had a swelling on
seat of inoculation for three clays with lameness and a rise of
temperature to 39.6°C. ; these bulls showed no disturbance
after the inoculation of the virus.
In the above experiments the mixed vaccine (c) gave
much superior results to both Blacklegoids and vaccine (b)
and protected in every case. The Laboratory test applied,
namely, the intramuscular inoculation of 1 c.c. of a solution of
0.2 gm. dried muscle juice dissolved in. 5 c.c. N. S. S., is un-
doubtedly a much more severe trial than natural infection.
In the latter case the mortality is comparatively low,
seldom over 30%, and the duration of the disease in fatal cases