NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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The. cultiva-
tion of lacilli
from the
blood.
At some laboratories (for example at the Central Research Institute at
Kasauli in India) one can obtain small bottles containing a proper quantity
of a medium called Conradi's ox-bile medium which is very suitable for the
cultivation from the blood of the bacilli of typhoid and allied fevers. By
the use of this method it is possible for a diagnosis of enteric fever to be
made on the first or second day of the disease, which is very much earlier
than is possible by the use of the serum test. All the physician in charge of
the case has to do is to withdraw about two or three cubic centimetres of
blood under strictly aseptic precautions from the patient and transfer it to
the bottle of medium which is then returned to the laboratory. To collect
the blood one needs a syringe marked in cubic centimetres.* The following
are the directions furnished with the bottles of medium sent out from the
Central Research Institute in India : (1) the front of the bend of the patient's
elbow is sterilized with 1 in 20 carbolic lotion which is removed with alcohol
and ether ; (2) a vein is made prominent by pressure at the bend of the
elbow ; (3) a syringe and needle having been previously sterilized by boiling,
the needle is introduced into the prominent vein and two and a half cubic
centimetres of blood are withdrawn ; (4) the blood is immediately injected
into the bottle of medium by passing the needle through the rubber cap
which closes the mouth of the bottle ; (5) the small hole made by the needle
in the rubber cap is sealed by melting the paraffin which covers it. This can
be done with a lighted match ; (6) the bottle is shaken, labelled, and returned
to the laboratory with particulars of the case.†
4.—The examination of the sputum and of the fæces,
The tubercle
bacillus.
The practitioner who desires to make no mistake in the diagnosis of cases
of malarial fever must know how to examine the sputum for the presence or
absence of tubercle bacilli and how to examine the fæces for the presence or
absence of the eggs of different kinds of worms.
*2 c. c.=34 minims, approximately, and 3 c.c.=50 minims, approximately.
† If the operation of obtaining blood from a vein does not appear justifiable, sufficient
blood can usually be obtained by puncturing the lobe of the car. It is not essential to
employ exactly 2½ c. c. of blood, but the amount should never be less than 1 c. c. The opera-
tion of obtaining blood from a vein is, however, an exceedingly simple and almost
painless one, which if once carried out will always be preferred to the sometimes difficult
and often painful endeavour to obtain 2 or 3 c. c. of blood by stabbing the ear or
finger.
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The following are the necessary directions regarding the examination for
tubercle bacilli in sputum * or in pus :—
(1) Make a thick film on a slide.
(2) Dry it in the air and fix it by immersion in absolute alcohol for
15 minutes.
(3) Heat some carbol fuchsine stain in a test tube nearly to boiling
point and pour it on the film, taking care that the film is well
covered, but that none of the stain spills over the edges of the slide.
(4) Hold the slide over a spirit lamp so that the stain keeps steaming, but
not boiling, and allow the stain to remain on the film for ten
minutes.
(5) Wash the film in water.
(6) Pour a 25 per cent. solution of sulphuric acid on the film to
decolourize it until it is lightly pink.
(7) Wash the film in water.
(8) Stain the film with Loeffier's methylene blue for two minutes.
(9) Wash in water, dry, and examine with a one-twelfth inch oil
immersion objective.
Eggs of
intestinal
worms.
The only directions that need be given regarding the examination of faeces
for ova of intestinal worms are that the portion of fæces which is placed on the
slide should be very minute and should be mixed with water so that when the
cover glass is applied the layer will be very thin ; it is little use trying to
identify eggs in a thick film of fæces. The specimen should be examined with
a two-third inch objective. The appearance of ova of the three more common
intestinal worms is so definite and characteristic that, with the aid of the
diagrams in Plate II, a, 6, c, there should be no difficulty in identifying them.
5.—The study of mosquitoes,
The general appearance of a mosquito is probably well known to all,
but it may be necessary to mention that mosquitoes may be distinguished
from other flies (such as " sand-flies," etc.) which seem to resemble them,
by the following characters :—
(1) They have a long sucking proboscis.
* Tubercle bacilli are usually more abundant in the first sputum coughed up in the early
morning.
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(2) The veins of the wings are covered with scales (which can be
plainly seen with a small magnifying glass). The veins of the
wings of other flies have no scales.
The melamor-
phosis of
mosquitoes.
The following are the stages through which mosquitoes pass before they
reach the adult state. An adult female mosquito lays its eggs on a pool or
other collection of water. In a few hours these eggs hatch into small worm-
like wriggling animals called larvæ, whose life is spent entirely in water.
After a variable time, depending chiefly on the temperature, the larvæ
change their shape and character, and become small comma-shaped creatures
called pupæ which spend their time struggling to the bottom of the
water and floating up to the surface again to breathe. After one or
two days the pupæ are transformed into the adult insect or imago, which
emerges at the surface of the water from the skin or pupa-case en-
closing it, and which it leaves behind in the water. After resting for
a while on the surface of the water, the adult mosquito flies away to
seek its food. The study of mosquitoes therefore includes the study of their
ova, larvæ, pupæ and imagines.
Classification.
Species,
genera, and
sub-families.
For purposes of classification and identification the family of insects
called Culicidæ or mosquitoes has been separated by entomologists into
groups of species, genera and sub-families. Thus, if a large collection of
mosquitoes were in the hands of an entomologist for examination, he would
note in the first place that some of the individuals were of exactly the
same appearance and could not be distinguished from one another ; for this
reason he would say that all such individuals were of the same species or
kind. Next he would examine specimens of different species and would
find that although the individuals of one species could be distinguished from
those of another (because, let us say, the legs or wings presented different
colour markings) yet the mosquitoes of perhaps two or three species
possessed an important anatomical character in common, while the mosquitoes
of two or three other species did not possess this character. He could,
therefore, classify the different species in a number of groups or genera, each
genus containing the different species which possessed an important
anatomical character in common. Finally, by examining mosquitoes in
different genera, he might find that the members of one genus were quite
different in an obvious and important anatomical manner from the members
( 25 )
of another genus and so on these grounds could group the mosquitoes in
the different genera in perhaps two or three or more sub-families.
The sub-
family
Anophelinæ
is most
important.
This plan of classification simplifies the subject, and at present the 700
or 800 species of mosquitoes which are known have been classified in
109 genera and 10 sub-families. It is obvious that if such a classification is
founded upon anatomical characters which are constant and easy to observe,
there should be no difficulty in ascertaining first the sub-family and then the
genus of any particular mosquito, and that since the number of species in
any genus is, as a rule, small, we ought to be able to name any mosquito
correctly without much difficulty. So far as the student of tropical medi-
cine is concerned, it is fortunate that only two sub-families of mosquitoes
(namely, the sub-families Anophelinæ and Culicinæ) are known to act as
carriers of human disease and that the members of only one sub-family, the
Anopheline, act as carriers of the malaria parasites.
For our present
purposes, therefore, we have to deal with the Anophelinæ only, and it may
be said at once that the characters of mosquitoes in this sub-family are such
that there is no difficulty in distinguishing a malaria-carrying from a non-
malaria-carrying mosquito. In dealing with this subject we shall discuss first
the collection, examination and identification of adult Anopheline mosquitoes.
How to collect adult Anopheline mosquitoes.
One of the habits of Anopheline mosquitoes is that they fly about only
after dusk and during the night ; in the daytime they seek some dark shed,
outhouse, or stable, where they rest on the walls and roof. In these
places they can be easily caught, the necessary implements being a
few dry test tubes, a large dry bottle and some cotton wool. When a
mosquito is seen resting on the wall or roof, the mouth of a test tube is
placed very gently over it. It will fly into the tube, the mouth of which
can then be closed with a plug of cotton wool. Each mosquito caught
may be transferred to the large glass bottle by placing the mouth of the
tube over that of the bottle and removing the cotton wool plug. The
mosquito will fly into the large bottle, and the tube can be used again. If
Anophelinæ are at all abundant, twenty or thirty can be caught in this way
in a very short time. The best places in which to search for them are
outhouses, cowsheds, woodsheds, and thatched unoccupied rooms with
dirty smoke-blackened walls and many cobwebs. It is almost useless to
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The
appearance of
Anophelines.
search in a freshly whitewashed house. Even in places which appear
favourable, Anopheline mosquitoes are often difficult to detect, and some
species hide among the straw of a thatched roof or in holes and corners of
the wall with great success. For searching the roof a ladder should be
used, so that the eye is not more than a foot or so off the roof, and every
part of the thatch should be carefully examined. Two characters of
Anopheline mosquitoes are of great service to the collector ; they are (1) the
structure of an Anopheline is such that an imaginary line drawn along
its proboscis and through its head, thorax and abdomen is practically
straight, and for this reason it happens that if an Anopheline is resting on a
wall with the tip of its proboscis touching the wall the hinder end of the
insect projects outwards so much that the insect appears to be standing on
the tip of its proboscis. Thus, in a dark outhouse or hut the commoner
Anophelines (which are light coloured) stand out against the dark back-
ground of dirt and soot, looking like little white thorns stuck in the wall or
hanging from the roof. On the other hand an imaginary line drawn through
the proboscis, head, thorax and abdomen of any other mosquito than an
Anopheline would not be straight, but would slope upwards to a point near
the top of the thorax and then downwards to the end of the abdomen, thus
forming an angle. For this reason when such a mosquito is resting on
a wall with the tip of its proboscis touching the wall the anal end of
the abdomen is also nearly touching the wall and the insect appears " hunch-
backed." (2) As a general rule most Anopheline mosquitoes have spotted
wings whilst the wings of most other kinds of mosquitoes have no spots.
How to mount, examine and identify adult Anopheline mosquitoes.
The mosquitoes that have been caught should be killed by placing a
drop or two of chloroform on the muslin cover of the bottle. The dead
mosquitoes are then turned out on to a clean white sheet of paper and
mounted as quickly as possible.
The following articles are necessary for mounting a mosquito —
(1) A supply of fine silver pins, No. 20 size.
(2) A pair of forceps for holding the pins.
(3) Small discs of thin cardboard.
(4) Ordinary pins.
(5) A box in the bottom of which a layer of cork or pith is fixed.
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Mosquitoes which are required for identification should never be touched
with the fingers. A pin or needle should be used for moving them when
this is necessary. A card-disc should be taken, and one of the No. 20 silver
pins thrust through its centre, so that about half the pin projects each side.
The mosquito to be mounted is turned over on to its back, and the point of
the pin carrying the disc is entered into its thorax at the point of origin of
the legs, and made to emerge through the dorsum of the thorax. On turn-
ing the disc over, the mosquito will be found to be mounted in its natural
position, right side uppermost, and its legs and wings can be gently arranged
on the card-disc with the aid of a pin. An ordinary pin is now thrust
through the edge of the card-disc to attach it to the cork in the bottom of
the box. (See figure.)
METHOD oF MOUNTING A MOSQUITO.
A. pin through card-disc, B ; C. label for date, locality, etc.; D. No. 20 pin through
card-disc (B) and mosquito (F) ; E. point of D through thorax of mosquito.
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Examination
of mosquitoes.
For the proper examination and identification of adult mosquitoes a low
power microscope is almost a necessity, but in the absence of this it will be
found that most of the markings and characters, except those relating to the
shape of the scales, can be made out, though less easily, with a hand-lens.
For the examination under a microscope, the mosquito, which has
already been mounted on a card-disc in the manner above described, is
fixed by a pin thrust through the edge of the disc to a flat piece of cork
about an inch square. This cork is placed on the microscope stage and can
be moved about at will, so as to bring all parts of the mosquito under the lens.
The different parts of the external anatomy which the student must
learn to recognise are shown in Plate III. It is best to begin by examining the
antennae, proboscis, and palpi, because it is by the examination of these
structures that one can tell firstly whether the mosquito is a male or female,
and secondly whether it belongs to the sub-family Anoplielince or not.
To ascertain the sex of a mosquito examine the antennæ. In male
mosquitoes the antennas are covered with long hairs so that each antenna
forms a feather-like tuft in. front of the head. In female mosquitoes the
antennæ have no long hairs and are nearly bare. (Plate IV, h. and f,)
The sex is often obvious to the naked eye when, for example, the
abdomen is distended with eggs or with blood. It is important to make no
mistake in the sex of a mosquito because since only female mosquitoes suck
blood they are the only ones which can carry malaria parasites and the only
ones which we need to study.
To ascertain whether a mosquito is an Anopheline examine the antennæ,
the proboscis and the palpi—
(1) Examine the antennae to make sure that the specimen is a female.
(The student of tropical medicine need not complicate the
subject by dealing with male mosquitoes.)
(2) Examine (a) the proboscis and (b) the palpi. If the proboscis is
straight and the palpi are as long or nearly as long as the pro-
boscis the mosquito must be an Anopheline.
These two characters, namely, a straight proboscis and palpi as long or
nearly as long as the proboscis, are present in the females of no other kind
of mosquito than an Anopheline.
PLATE III
DIAGRAM
OF A
FEMALE
ANOPHELINE.
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A detailed
examination
is necessary
for identifica-
tion.
Having ascertained that the specimen belongs to the sub-family Anophe-
lince the student will proceed with the minute examination necessary for
making a complete identification of the mosquito. In the examination of
the palpi it will be noted whether they are densely scaled or not and whether
they are uniformly coloured or encircled with white bands, and the number,
relative size, and position of such bands will be carefully described. In addi-
tion to definite bands a few white scaled patches may be present (as
" speckling ") on one or more segments of the palpi. Passing on to the
examination of the head the characters of the scales will be noted, and in
particular the characters of the upright forked scales (Plate IV, g & l) can
be readily made out. In most Anophelines a prominent tuft of white hairs
projecting forwards from the anterior end of the head will be seen. The
thorax will next be examined, and it will be noted whether the dorsum is
covered with scales or with hairs or with both, and the characters of these
structures will be described. Passing on to wards the abdomen the scutellum
will be examined ; it will be seen that it is always simple—never trilobed as
in all other sub-families of the Culicidce—and that it carries scales or hairs.
The bare horse-shoe shaped metanotum or post-scutellum will next be seen,
and then the halteres, the knobs of which are clothed with numerous small
scales. The examination of the abdomen is of great importance. In some
species, although the abdomen is thickly covered with long hairs, no scales
are present. In other species it will be seen that in addition to the hairs
covering the majority of segments a few scales can be discovered on the ventral
surface of the last one or two segments only.
In other species, again, it
will be seen at once that the dorsum of each segment is thickly set with
white or golden-brown scales which in some species are very broad and in
others more or less spindle-shaped. (Plate IV, q & s.) It will readily be
recognised that the presence or absence and the character of these scales
is very important.
The wings and legs will next be examined. The best way to describe
the wings is to make a diagrammatic drawing showing the number and
relative width and position of the different dark and light-scaled areas on
each vein. (Plate IV, i.) The shape of the wing scales must be noted by
separate examination of a wing mounted under a cover glass.
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A. careful description of the markings on each leg, commencing with those
on the femur and ending with those on the fifth tarsal segment, should be
made. In some species complete bands of white scales encircle the legs near
the joints, and the position of these bands should be noted. In addition
small patches of white scales will be found in some species on certain seg-
ments of the legs (''speckling") and in some species one or more of the
terminal tarsal segments of the hind legs will be found to be white-scaled in
their whole length.
Finally the ungues, sharp-pointed horny structures attached to the tip of
the fifth tarsal segment of each leg, will be examined.
Generic dif-
ferences arc
founded upon
scale charac-
ters.
The description being completed we must attempt to classify the mosquito
in its correct genus and species. At present the shape and arrangement
of the scales found on the head, thorax, abdomen and wings of mosquitoes
are the anatomical characters upon which the distinctions between the
different genera in the sub-family Anophelinæ are based, but there
are many who maintain that a generic grouping founcled upon these
characters is not satisfactory, and the matter is not yet settled. The subject
of scale structure, however, is interesting, and, with the saying clause
that the opinions now held by entomologists on the matter are liable to
correction as a result of future work, we may give here a brief sum-
mary of the characters by which the different genera in the sub-family
Anophelinæ met with in India are distinguished from one another. These
genera are :—
1. Anopheles.
2. Myzomyia.
3. Stetliomyia.
4. Pyretophorus.
5. Myzorhynchus.
6. Nyssorhynchus.
7. Cellia.
8. Ncocellia.
The shape and arrangement of the scales and hairs on the thorax and
abdomen serve as the primary characters by which these genera are distin-
guished, and our examination must be directed firstly to these regions. So far
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as they are concerned the following table indicates the characters of the
different genera:-—
Genus.
Anopheles .
Myzomyia.
Stethomyia
Myzorhynchus.
Pyretophorus
Nyssorhynchus .
Cellia
Neocellia .
Thorax.
Hair like curved scales
(Plate IV, p)
Hair like curved scales
Hair like curved scales
Hair like curved scales
Narrow curved scales (Plate
IV, o).
Narrow curved and spin die-
shaped scales. (The latter
somewhat as in Plate IV,
8.)
Flat spindle-shaped scales .
Flat spindle-shaped scales.
Abdomen.
Hair like curved scales.
Hair like carved scales.
Hair like curved scales.
Hairs on the dorsal surface, but a dis-
tinct tuft of scales on the ventral
surface of the terminal segment.
(Shaped as in Plate IV, o, q or r. )
Hairs.
Small tufts of flat scales on the dorsum
and a, few tufts projecting laterally.
Nearly completely covered with scales
(shaped as in Plate IV, g) irregularly
disposed on the dorsum and dense
tufts projecting laterally.
As in Cellia, but no lateral tufts.
It will be seen that the characters of the genera Anopheles, Myzomyia
and Stethomyia in the above table are the same, and we must therefore search
for minor distinguishing characters.
According to Mr. Theobald these characters are :—
Anopheles
Myzomyia
Stethomyia
Wing scales large and lanceolate in
shape. (Plate IV, r.)
Wing scales mostly small, long and
narrow, or slightly lanceolate.
In
addition to the upright forked
scales present on the head of all
Anophelince there are some flat
scales (Pate IV, s and t) on the
median area of the head. These ara
not present in any other genus.
Wing scales lanceolate in shape.
The genus Myzorhynchus is not difficult to recognise because in addition
to the characters already given, the palpi are thickly scaled and the wing scales
are very large and lanceolate in shape,
PLATE IV.
Line Block.
Survey of India Offices, Calcutta, 1908.
a, Egg of Anopheline; b, larva of a "culex" mosquito; c, larva of an
Anopheline mosquito; d, a palmate hair much, magnified; e, pupa of an Anopheline
mosquito; f, head of a female Anopheline mosquito; g, the upright forked
scales at the back of the head, magnified; h, head of a male Anopheline mosquito;
i, wing of the Anopheline called rossii; j, the scales of the wing fringe,
magnified; k, the lanceolate shaped scales of the wing; l, upright forked
scales; m, twisted scale; n, broad curved scale; o, narrow curved scale; p, hair
like curved scale; q, blunt ended lanceolate scale; r, sharp pointed lanceolate
scale; s, spindle shaped scale; t, broad flat scale.
( 33 )
In the genus Pyretophorus no scales at all can be found on the abdomen,
only hairs being present.
The three remaining genera are not difficult to distinguish by the charac-
ters of the abdominal scales.
The Anopheline most commonly met with in India, namely rossii, cannot
be placed in any of the above genera, and a new genus called Pseudomyzomyia
is to be created for it.
If the student succeeds in placing in its correct genus any specimen
which he wishes to identify, the remaining portion of his task will be
comparatively easy, for there are only a few Indian species of Anophelines
in each genus. They are the following :—
In the genus Anopheles : —
In the genus Myzomyia : —
In the genus Stethomyia : —
In the genus Myzorhnchus : —
In the genus Pyretophorus : —
In the genus Nyssorhynchus :—
In the genus Cellia : —
In the genus Neocellia : —
(1) gigas.
(2) lindesayii.
(3) aitkenii.
(4) immaculatus.
(1) listoni.
(2) culicifacies.
(3) turkhudi.
(1) culiciformis.
(1) barbirostris.
(2) nigerrimus.
(1) nigyrifasciatus.
(2) jeyporiensis.
(3) elegans.
(1) maculatus.
(2) stephensi.
(3) willmori.
(4) karwari.
(5) theobaldi.
(6) maculipalpis.
(7) jamesii.
(8) fuliginosus.
(1) pulcherrima.
(2) punctulata.
(1 ) indica.
(2) dudgeonii.
(3) intermedia.
Species described by Mr. Theobald from only one specimen are not
included in this list.
D