HALTENHOFF. A. f. A., xiv, 1885. GRIFFITH. T. O. S., xx, 1900. CHEATHAM.
A. of O., xxv, 1896. LAWFORD. Brit. Med. Jl., 1901. BYERS. Montreal Med. Jl., 1902.
NEUBURGER. K. M. f. A., xli, 1903. MORAX. These de Paris, 1894. LOEB. Deutsch.
Arch. f. klin. Med., xxxii, 1886. KOENIG. Berl. klin. Woch., 1897. NEISSER AND BUMM.
Wien. klin. Woch., 1897. GIELEN. Inaug. Diss. Bonn., 1897. DEUTSCHMANN. A. f.
O., xxxvi, i, 1890. CLEMENT LUCAS. Trans. R. Med.-Chir. Soc., Ixxxii. ALTLAND. K.
M. f. A., xl, 1902. E. v. HIPPEL. A. f. O., xlvii, 1899. LEBER AND ADDARIO. A. f. O.,
xlviii, i, 1899. PARISCHEFF. Nagel's Jahresbericht, 1892. NIEDEN. K. M. f. A., xxix,
1891. GONIN. Rev. med. de la Suisse Romande, 1899. *GROENOUW. A. f. O., Hi, i,
1901. EPERON. Les Affections blennorrhagiques de 1'CEil, Lausanne, 1902. MENGE AND
KROENIG. Bakteriologie des weiblichen Genitalkanals, Leipzig, 1897. WILBRAND,
SAENGER, AND STAEHLIN. Jahresb. d. Hamburger Staatskrankenanstalten, iii, 1891-2.
KRUKENBERG. K. M. f. A., xxxvii, 1899; xxxviii, 1900; xxxix, 1901. ABELSDORFF AND
NEUMANN. A. f. A., xlii. 1900. URBAHN. A. f. A., xliv, Erganzungsheft, 1901. WILDHOLZ.
A. f. Derm., 1902. KAYSER. K. M. f. A., xli, Beilageheft, 1903. FRANKEL. Z. f.
Hygiene u. Infectionskrankheiten, xxxi, 2, 1899. HAGLUND. K. M. f. A., xxxviii, Beilage-
heft, 1900. MORAX AND ELMASSIAN. Ann. d'Oc., cxxi, 1899; Verhandl. d. internat. Ophth.
Kongr., Utrecht, 1899. DAHLSTRONN, K. M. f. A., xli, 1903, Beilageheft.
THE KOCH-WEEKS BACILLUS
The commonest cause of acute contagious conjunctivitis seems to
be the Koch-Weeks bacillus. It was discovered by Koch in Egypt in
1884, and was wrongly regarded by him as a concomitant of Egyptian
ophthalmia. It was rediscovered by Weeks in New York in 1885, and
proved by him to be the cause of an acute contagious conjunctivitis,
which had no relationship with trachoma. Kartulis found it again in
Egypt in 1887, and Wilbrand, Saenger and Staehlin in Hamburg
in 1891. Since then it has been discovered almost everywhere Morax
(1894) in Paris, Juler (1894) in England, Gasparrini (1896) in Italy,
etc., so that failure to find it in certain places by Gifford, Axenfeld,
Fuchs, etc., is probably due to chance. It has been most thoroughly
and most successfully investigated by Morax.
The bacillus mostly attacks young people up to twenty years old,
but it occurs at all ages. It causes an acute muco-purulent con-
junctivitis ; no follicles are formed, but it frequently attacks the
sufferers from phlyctenular conjunctivitis. The cornea is rarely
affected, and then only by small grey superficial infiltrates ; central
THE CONJUNCTIVA 45
perforation has been described once (Morax and Petit). The pre-
auricular glands are sometimes enlarged. It has been found in the
new-born (Panas, Coppez) ; Coppez' case was pseudo- membranous.
The bacilli are best stained by fixing the film with sublimate, and
subsequently washing out (less well by heat), and then treating with a
carbolised solution of methylene blue or methyl violet. They are
found lying between the leucocytes, and also within the protoplasm.
They very nearly resemble the bacilli of mouse-septicaemia, but are
thinner. They appear as very short fine rods (o'8 2ju), staining less
deeply than the nuclei of the cells (Fig. 20). They are often found
lying end to end, so as to form chains of two or three links, or side by
side. The ends are rounded, and often show a deeper polar staining.
The number varies greatly according to the period and intensity of the
FIG. 20. KOCH-WEEKS BACILLI, x IQOO.
Photograph by Henderson. Film from conjunctival sac.
infection. They are often found in almost pure culture, but not infre-
quently diplococci are also present. In these cases it is not uncommon
to find follicles in the conjunctiva (Wilbrand, Saenger, and Staehlin).
They are decolourised by Gram's method. These characteristics
render diagnosis by films easy.
Cultures are difficult, but a nearly allied form grows more easily
(v. infra, Weichselbaum and Miiller). The bacillus rarely grows on
gelatine or serum, occasionally on agar (after two days), best on 0*5 per
cent, agar, or the culture media most suitable for gonococci. It is
essential that the agar should be very moist. The more virulent the
conjunctivitis, the better are the cultures. Owing to the consistency of
0*5 per cent, agar, cultivation is best carried out in Petri dishes. After
keeping at 35 Celsius, very fine, scarcely perceptible granulations
appear on the surface after twenty-four to thirty-six hours. These
transparent colonies very much resemble those of the influenza bacillus.
Besides these there are larger, greyish, more opaque colonies. These
contain bacilli which stain with Gram, and generally show club-shaped
involution forms. The club-shaped bacilli occur in other forms of con-
junctivitis (ophthalmia neonatorum, etc.). They are easily isolated
from the pure Koch-Weeks bacilli, but it is difficult to obtain the latter
without the former (Greeff). It is best effected by inoculating the
condensed water in a tube, and then making a second and third similar
inoculation, finally spreading the water on the surface of the medium.
Morax has succeeded in obtaining cultures on the ordinary media, but
this usually fails. Subcultures always fail after the fifth day, and often
before; Morax only obtained two or three generations on 0*5 per cent,
The bacilli in cultures are non-motile, stain faintly with aniline
dyes, and are decolourised by Gram. They cease to stain after a few
weeks. They occur in clumps, and are mostly short, like those in the
conjunctiva; but others, two or three times as long, occur.
Weeks failed to obtain positive results by inoculation in men and
animals. Morax failed with animals, but succeeded with men. There
is an incubation period of two to three days ; the opposite eye usually
becomes infected two or three days later. The inflammation reaches
its height at about the sixth or seventh day. On the first day, only
few bacilli can be found ; after the third they are numerous ; cauterisa-
tion with silver nitrate (0*5 per cent.) on the sixth day led to great
diminution of the bacilli on the ninth day, and to total absence on the
Microscopic sections of the conjunctiva, removed on the third day,
showed ordinary lymphocytic infiltration, vascular congestion, and
dilatation of lymphatics. The epithelium was intact. Sections stained
by carbol-thionin and w r ashed out with absolute alcohol (Nicholle's
method) showed groups of bacilli in the superficial layers of the epithe-
lium, and deeper amongst the leucocytes. There were none in the
It is doubtful if the Koch-Weeks bacillus can give rise to a chronic
conjunctivitis, but the investigations of Hoffmann, and of Weichsel-
baum and Muller tend to show that it can. The latter authors have
obtained rather different results from Morax, chiefly with regard to
details of cultivation. They compare the bacillus to that of influenza,
and to Miiller's trachoma bacillus (v. "Trachoma"). It is probable
that the bacillus found by them is only a modified form of the Koch-
KOCH. Wien. med. Woch., 1883; Arbeiten a. d. kaiserl. Gesundheitsamt, iii, 4, 1884.
WEEKS. A. of O., xv, 1886. KARTULIS. Centralbl. f. Bakteriologie, i, No. 40, 1887.
WILBRAND, SAENGER, AND STAEHLIN. Loc. cit., 1891-2, 1894. MORAX. These de Paris,
1894. JULER. Brit. Med. Jl., 1894. STEPHENSON. Epidemic Ophthalmia, London. 1896.
GASPARRINI. Ann. di Ott., xxv, 1896. MORAX AND BEACH. A. of O., xxv, 1896. MORAX
AND PETIT. Ann. d'Oc., cxx, 1898. MORAX AND ELMASSIAN. Ann. d'Oc., cxxi, 1899.
PANAS. Congres d'Opht. Paris, 1891. ELMASSIAN. Ann. d'Oc., cxxii, 1900. GREEFF.
In Orth's Lehrbuch., Berlin, 1902. RYMOWITSCH. Wratsch, xx, 1900-1. MARKUS.
Munch, med. Woch., 1901. HOFFMANN.- Z. f. Hygiene und Infectionskrankheiten, xxxiii,
1900. KAMEN. C. f. Bakt., xxv, 1899. WEICHSELBAUM AND MULLER. A. f. O., xlvii, i,
1898. MULLER. A. f. A., xl, 1899; A. f. O., Ivii, i, 1903.
THE MORAX-AXENFELD DlPLOBACILLUS
The diplobacillus discovered independently in 1896 by Morax and
Axenfeld is the cause of one of the commonest forms of catarrhal
conjunctivitis. It occurs at all ages, but especially in adults. It is
characterised by a chronic, not very severe blepharo-conjunctivitis,
without follicles or membrane, but with a typical erythema of the edges
of the lids, with slight maceration of the skin, most marked at the
angles, especially the inner angle (angular conjunctivitis). The secretion
is watery and not copious. Superficial infiltration of the cornea is not
uncommon (Peters), and this also contains the organism (Morax and
FIG. 21. DIPLOBACILLI (Morax-Axenfeld). x 1000.
Photograph by Henderson. Film from conjunctival sac.
Petit, Petit [i]). The conjunctivitis is rapidly cured by zinc sulphate
lotion, but shows no tendency to spontaneous cure.
The diplobacillus is apparently found in all countries, and is
extremely contagious. Eyre found it in 2.\ per cent, of all the patients
in Guy's Hospital eye clinic, and it is equally prevalent elsewhere.
Biard found it simultaneously in the nose. In 310 cases of catarrhal
conjunctivitis Gonin found the diplobacilli 185 times, Koch- Weeks
bacilli 10 times, pneumococci 10 times, streptococci 5 times, Staph.
aureus 83 times.
Cover-glass preparations are quite characteristic (Fig. 21). The
bacilli are generally very numerous ; they are large (2 /j. by I ^t, but this
varies considerably), generally occur in pairs, and often in chains.
They are decolourised by Gram's method. They do not possess a well-
defined capsule, but this is sometimes present (Gifford, Hoffman, zur
48 THE PATHOLOGY OF THE EYE
Nedden). A fine capsule can be demonstrated ordinarily by special
capsule staining (Bietti).
Cultures are obtained with some difficulty, and only on blood-
serum, serum-agar, or the usual media for gonococci. Blood-serum is
liquefied. Cultures on serum-agar form minute transparent spots, not
unlike pneumococcus cultures. The agar is not liquefied. The diplo-
bacilli grow best on alkaline media, and are obligate aerobes ; they are
The diplobacillus of Morax is not pathogenic for animals, but is
readily transferred from pure cultures to the human conjunctiva, the
incubation period being about four days.
Allied to the Morax-Axenfeld bacillus is the Bacillus liquefaciens (Petit
). It is a diplobacillus, i /m 17,11 by 0*8 /u i n, the diplo-form
FIG. 22. DIPLOBACILLI (Morax-Axenfeld). x 1000.
Photograph by Henderson. Culture, by Eyre, on serum-agar, eight days,
showing involution forms.
being constant. It occurs in some superficial ulcers of the cornea,
accompanied by slight iritis and hypopyon (McNab). McNab found
capsules, which were not seen by Petit. It gives a negative reaction
with Gram. It grows on all ordinary media, has a low power of
resistance to heat, but considerable to dryness. It liquefies gelatin in
stab cultures at 15 20 C., but on cultivation this power appears to be
lost (McNab). It rapidly liquefies blood-serum, in this respect
differing from Friedlander's and zur Nedden's bacilli (q. v.). It differs
from the Morax-Axenfeld bacillus in growing readily on pure agar.
MORAX. Ann. de 1'Institut Pasteur, juin, 1896; Ann. d'Oc., cxvii, 1897. AXENFELD.
B. d. o. G., 1896; Centralbl. f. Bakteriologie, xxi, 1897; Berl. klin. Woch., 1897. PETERS.
K. M. f. A., xxxv, 1897. BIARD. These de Paris, 1897. GONIN. Rev. med. de la
Suisse Romande, 1899. BACH AND NEUMANN. A. f. A., xxxvii, 1898. MORAX AND PETIT.
Ann. d'Oc., cxx, 1898. PETIT (i). These de Paris, 1900. EYRE. Brit. Med. Jl.,
THE CONJUNCTIVA 49
GIFFORD. Annals of Ophth., vii, 1898. HOFFMANN. A. f. O., xlviii, 3, 189^. LOBANOW.
A. f. O., li, 3, 1900. ZUR NEDDEN. K. M. f. A., xxxix, 1901. PFLUGER. Korre-
spondenzbl. f. Schweizer Aerzte, 1902. BIETTI. Ann. di Ott., xxviii, 2, 1899. PETIT (2).
Ann. d'Oc., cxxi, 1899 ; Recherches clin. et bacteriol. sur les Infections aigues de la Cornee,
1900. McNAB (working under Axenfeld). Personal communication ; K. M. f. A., xlii, 1904.
THE DIPHTHERIA BACILLUS (KLEBS-LOFFLER)
Membranous conjunctivitis was mentioned by Mackenzie in 1845,
and possibly still earlier by Wharton Jones. It was not, however, until
1854 tnat von Graefe gave a satisfactory description of the severer type.
It is a mistake to ascribe the account of the milder or croupous form to
the earlier writers Bouisson and Chassaignac (1846) (Coppez [i]).
FIG. 23. DIPHTHERIA BACILLI, x 1000.
Photograph by Henderson. Culture, by Eyre, on blood-serum, eighteen hours.
Babes, in 1886, first discovered the Klebs-Loffler bacillus in the con-
The type of conjunctivitis caused by the diphtheria bacillus varies
much ; it is almost always membranous, but both its local severity and
the severity of the general symptoms differ enormously. This is
acknowledged by an overwhelming consensus of opinion. On the other
hand, there is an equally wide agreement that membranous con-
junctivitis (q. v.) is caused by many other agents, both chemical and
bacteriological. In thirteen cases of membranous conjunctivitis Gonin
found the Klebs-Loffler bacillus seven times, staphylococci four times,
pneumococci once, and Koch- Weeks bacillus once. In most cases of
true diphtheria, other organisms, especially staphylococci and strepto-
cocci, are found besides the Klebs-Loffler bacillus, and probably the
nature of the mixed infection, combined with variability in the reaction
50 THE PATHOLOGY OF THE EYE
of the patient's tissues, determines whether the membrane will be
merely superficial and benign, or deeply necrosing and malignant. It
may even be absent ; such cases are described in diphtheria epidemics,
and in cases of membranous conjunctivitis in the other eye (Sourdille,
Uhthoff, Aubineau, v. Hippel, Pichler, Copper). The idea that the
longer forms of the bacillus are most virulent (Martin) cannot be
substantiated (Sourdille, Morax, etc.)- There can be no doubt that
the condition of the tissues is of great importance that the diphtheria
bacillus, in fact, is only conditionally contagious for the conjunctiva.
This is seen clearly in rabbits, in which inoculation into the normal
conjunctival sac fails if the epithelium is uninjured. Uhthoff, indeed,
considers previous conjunctivitis essential in human beings, and
eczema of the lids is common in the croupous form (Schmidt-Rimpler).
The probability of Uhthoff s view is supported by Axenfeld, who points
out that virulent diphtheria bacilli have been found on the normal
mucous membrane of the throat. They have also been found in the
conjunctiva (Coppez, Pichler). The bacilli persist for a long time
during convalescence, and remain virulent (Sourdille, Uhthoff, Schirmer) ;
repeated attacks may occur, probably owing to the passing off of a
temporary immunity conferred by the previous attack. There is a rare
chronic recurring form (Valude, Arlt, Coppez, Morton), which is only
occasionally due to the Klebs-Loffler bacillus ; staphylococci have been
found, but the bacteriology has not been well worked out (see " Mem-
Mixed infection, e.g. with streptococci, does not necessarily cause a
severe type (Sourdille), but the majority of cases are worse than with
pure diphtheria. Uhthoff almost invariably found staphylococci and
streptococci, though the course of the disease was usually mild and
There is now ample evidence to show that antitoxin treatment is
very effectual in true diphtherial conjunctivitis (e.g. Jessop, Stephenson).
Many, however, agree that it fails to produce amelioration of corneal
inflammation, when that has supervened (Gonin, Uhthoff, Coppez ,
Wagner, Axenfeld). It has naturally been found to be less effectual
in severe mixed infections (e.g. with gonococcus, Wagner). Morax
and Elmassian have shown that membranous conjunctivitis can be pro-
duced in rabbits by dropping in diphtheria toxins, even without previous
injury to the conjunctiva; the cornea is also affected (Coppez ).
There is a definite latent period of twenty-four to twenty-eight hours.
These results lend reason to the suggestion that the antitoxin serum
should also be applied locally (Coppez , Mongour).
Randolph has found that continued instillations of the toxins of the
B. diphtheria and of other organisms (gonococcus, streptococcus,
Staphylococcus aureus, and B. xerosis), produced by filtration of sugar-free
bouillon cultures of varying ages, produced no reaction on the normal
conjunctivas of rabbits. If, on the other hand, small amounts of the
filtrates from even most recent cultures were injected into the tissue of
the conjunctiva, marked inflammatory reaction followed. This tends to
show that the bacteria are dependent in their action upon some lesion
of the conjunctiva.
THE CONJUNCTIVA 51
The subject is made more complex by the universal presence of the
xerosis bacillus. The relationship of the two organisms will be dis-
The diphtheria bacillus was discovered by Klebs in 1875, but was
only fully investigated, and proved to be pathogenic, by Loffler in 1884.
It stains well with methylene blue, and is not decolourised by Gram's
method. It is not quite so long as the tubercle bacillus, and rather
thicker ; but it occurs in very variable forms, straight or curved (Fig.
23). The extremities, which are more deeply stained, are often
slightly enlarged ; and this condition is often exaggerated by the forma-
tion of small, very deeply staining bodies at the poles, resembling
spores. The bacillus, however, does not form spores.
It grows best upon Loffler's blood-serum, 1 but also well upon serum-
agar, alkaline bouillon, etc. On solid media at temperatures from
20 42 C., it forms flat, greyish colonies in twenty-four hours. Involu-
tion forms are common in cultures, the bacilli appearing cut up into
small rounded masses, some of which have a smaller diameter than the
bacillus, others being larger and oval in shape. On glycerine agar the
rods are shorter and thicker than usual. Both morphologically and
physiologically production of acid, indol formation, etc. the bacilli
vary greatly, and this fact probably accounts for many of the so-called
pseudo-diphtheria bacilli. Special staining reactions, such as Roux'
and Neisser's (v. infra), are by no means specific.
Subcutaneous inoculation of guinea-pigs with bouillon culture kills
within thirty-six hours. A small patch of grey membrane is formed at
the site of inoculation, with inflammatory redema and haemorrhages
COPPEZ (i). Des Conjonctivites pseudomembraneuses, Bruxelles, 1897. BABES.
Prag. Med., 1886. GONIN. Rev. med. de la Suisse Romande, 1899. UHTHOFF. Comptes
rendus du XII Congres internat. de Me'd., Moskau, 1898; Vossius' Sammlung, ii, 5, 1898.
SCHIRMER. A. f. O., xi, 5, 1894. MORTON. T. O. S., xiii, 1893. PICHLER. B. z. A., xxiv,
1896. JESSOP. T. O. S., xxii, 1902. STEPHENSON. T. O. S., xxii, 1902. WAGNER.
Inaug. Diss., Giessen, 1898. AXENFELD. Munch, klin. Woch., 1898. COPPEZ (2). A.
d'O., xix, 1899. MORAX AND ELMASSIAN. Ann. d'Oc., cxxi, 1899; Verhandl. d. IX internat.
Kongr., Utrecht, 1899. COPPEZ (3). Verhandl. d. internat. Kongr., Utrecht, 1899; Z. f. A.,
ii, 1899, Beilageheft. COPPEZ (4). Rev. gen. d'O., 1897. MONGOUR. Ann. d'Oc., cxx,
1898. SOURDILLE. Rev. mens. des Maladies de 1'Enfance, 1895; A. d'O., xiv, 1894.
RANDOLPH. Bull, of the Johns Hopkins Hospital, xiv, 1903. BIETTI. K. M. f. A., xli,
THE XEROSIS BACILLUS (KUSCHBERT NEISSER)
The so-called xerosis bacillus much resembles the diphtheria bacillus.
It occurs extremely frequently in the normal conjunctiva, and in great
numbers in xerosis ; it is not, however, the cause of this complaint, but
the conditions then present are very favourable for its development.
The bacillus was discovered by Kuschbert and Neisser in 1883 in
twenty-five cases of xerosis in an orphanage at Breslau. It was dis-
covered independently by Leber in the same year, and this discovery
was confirmed by Schulz. Weeks, in 1887, failed to inoculate rabbits'
1 Three parts calf's or lamb's blood-serum, with i part of peptone-bouillon made from
veal and containing i per cent, grape sugar.
52 THE PATHOLOGY OF THE EYE
conjunctive from xerosis. Frankel and Franke, in the same year,
failed to transfer the disease from children to animals and children,
but regarded the bacillus as the cause.
The xerosis bacillus is identical morphologically with the diphtheria
and pseudo-diphtheria bacilli ; it is stained by ordinary aniline dyes
and grows on the same culture media, forming similar colonies. It
differs from the diphtheria bacillus in not producing an acid reaction
in neutral peptone-bouillon (Eyre), and, as we have seen, it is not
pathogenic for men or animals. Frankel regarded it as a non-virulent
diphtheria bacillus, similar to those found in the throat by Roux and
Yersin, which became virulent when mixed with streptococci ; they
failed to make this bacillus virulent by any method, but this result was
also obtained in the case of very attenuated diphtheria bacilli. The
failure to produce acid, described by Eyre, is only a question of degree,
as the xerosis bacillus produces a small amount in time (Axenfeld).
Like diphtheria, the bacillus varies in rapidity of growth and in form
on various culture media ; and, indeed, different forms occur in the con-
junctiva. One of the most important of these, described by Gelpke as
the cause of an epidemic acute catarrhal conjunctivitis and named the
Bacillus septatus, has been the subject of much dispute (Heinersdorff [i] ,
Axenfeld). Gelpke's results were founded upon 1559 patients ; the
catarrh showed typical swelling of the fornix as compared with
relatively slight chemosis of the ocular conjunctiva (" Schwellungs-
katarrh "). A pseudo-membrane was rapidly formed, and corneal ulcers
and iritis were common. The Bacillus septatus was found in all cases ;
morphologically and culturally the differences from the xerosis bacillus
are minimal. Gelpke relies upon the fact that he has succeeded in
transferring the infection to human conjunctivae. He regards the
catarrh as an attenuated diphtheria. Gelpke cannot be considered to
have proved the identity of his organism.
Neisser, in 1897, described a method of staining which he thought
definitely distinguished the xerosis from the diphtheria bacillus.
Cultures are made upon Loffler's blood-serum at 35 ; cover-glass pre-
parations are made after ten to twenty-two hours' incubation ; these
are stained for one to three seconds with acetic acid methylene blue, and
then for three to five seconds with Bismarck brown. True diphtheria
bacilli are stained brown, and the polar globules described by Ernst
are stained blue. The latter are not stained in xerosis bacilli. The
difference is only one of time (Schanz), for xerosis bacilli react in the
same manner after forty-six to forty-eight hours (Dotsch). Heiners-
dorff (2) investigated xerosis bacilli from sixty normal conjunctivae,
and never obtained the polar stain within twenty to twenty-four hours'
cultivation. Frankel considered that a negative result eliminated true
diphtheria, though the converse did not hold good ; he obtained a
positive result once with a pseudo-diphtheria culture, and three
times with a positive result the organism was not pathogenic for
guinea-pigs. Loffler, however, at the International Congress for
Hygiene in Madrid stated that the reaction sometimes failed with
true diphtheria bacilli, and this has been confirmed. Staining of
a few globules may be neglected; the characteristic polar staining must
THE CONJUNCTIVA 53
be general. The positive reaction certainly seems to be very rare
with xerosis bacilli, and it is so far useful as indicating treatment by
antitoxin whenever it is found.
The resemblance between the xerosis and the diphtheria bacillus
has led some to regard the former as merely a non-virulent type or
stage of the latter, whilst others and those the majority affirm their
independence. Schanz, who has paid much attention to the subject,
objects to the term " pseudo-diphtheria" bacillus, and prefers to call it
the non-virulent (ungiftig) Loffler bacillus. Practically all authors
agree that the two cannot always be distinguished morphologically
(Schanz, Heinersdorff, Axenfeld, Uhthoff, Pes, etc.). Similarly they
are indistinguishable by culture, though the question of acid formation
before referred to must be remembered, and the fact that the true