uly 1, 1886] 
growth in nutrient media affords as just a basis for distinc- 
tion between micro-organisms as difference in microscopi- 
cal appearance or other morphological characteristics. 
Koch’s comma-Bacillus is therefore diagnostic of the 
disease, and this fact has now placed in the hands of 
medical men the power of at once recognising a true case 
of Asiatic cholera, the isolation of the organism from 
others in the choleraic discharges and its cultivation in 
suitable media being alone needed. ‘The results of Koch’s 
researches, whether fully accepted or not, have not affected, 
nor are they likely to affect, the measures on which reliance 
alone can be placed for the prevention of outbreaks and 
spread of the disease. In the words of the Committee 
before alluded to, “ Sanitary measures in their true sense, 
and sanitary measures alone, are the only trustworthy 
means to prevent outbreaks of the disease, and to restrain 
its spread and mitigate its severity when it is prevalent 
‘Experience in Europe and in the East has shown that 
sanitary cordons and quarantine restrictions (under what- 
soever form) are not only useless as means for arresting 
the progress of cholera, but positively injurious.” 
The view that typhoid fever cannot arise de xovo, but 
is always propagated by a specific contagion from a 
previous case of the disease, is steadily gaining ground, as 
the number of epidemics where the disease has been 
definitely traced to specifically polluted air or water 
increases. In many other cases, although the specific 
pollution has not been definitely proved, the probabilities 
in favour of such a view have been very great. No 
micro-organism has yet been found which can lay claim to 
be regarded as the specific contagion of the disease, but 
we are in possession of so many facts concerning the 
mode of origin and spread of this disease, that any 
discovery of that nature would probably not greatly affect 
the measures now taken for its prevention. 
The etiology of diphtheria has lately received very 
careful study, but so far without the attainment of any 
results capable of exact formulation. It is not a disease 
invariably dependent on insanitary conditions, such as 
typhoid fever is, but that such conditions favour its spread 
and severity is more than probable. The far greater 
comparative frequency of diphtheria in rural districts than 
in large towns in this country is well known, and has 
been attributed to the presence in the air of the latter of 
the products of coal combustion. This view appears the 
more probable seeing that Continental cities, where wood 
and not coal is chiefly used as fuel, enjoy no such 
comparative immunity from the disease. Excessive 
moisture in the air of a house, whether arising from 
defective construction of the walls or roof, or from a water- 
logged soil, are conditions very often associated with 
diphtheria. The fact also that the disease is most pre- 
valent in the damper seasons of the year, when vegetable 
matter is undergoing decay and fungus life is most active, 
favours the theory that the specific contagium of this 
disease is a mould or fungus, which flourishes most 
strongly in a damp and smokeless air. It isa remarkable 
fact that diphtheria is sometimes associated with scarlet 
fever in one epidemic, the two diseases appearing to be 
interchangeable ; but this is a subject that requires further 
elucidation. The contagion of diphtheria is extremely 
ersistent and long-lived, clinging with great pertinacity to 
infected articles, so that every article which is likely to 
have become contaminated requires very thorough disin- 
fection, preferably by heat. There can be no doubt that 
school attendance is often a chief factor in the propagation 
of the disease amongst children. 
Koch’s discovery of the Bacillus tuberculosts, a micro- 
organism now proved to be the specific contagium of 
tubercular disease in men and animals, has_ placed 
tubercular phthisis in the category of contagious diseases. 
A peculiar disposition or tendency, whether hereditary or 
acquired, is no doubt wanted to enable the germ to take 
up its habitat in the human lung, but the fact that this | 
NATURE 
197 
idiosyncrasy can seldom be definitely recognised renders 
great caution necessary both on the part of members of a 
family in their association with a consumptive relation, 
and of hospital authorities in admitting into a general 
ward cases of tubercular disease, or of massing together 
into one institution patients in every stage of the disease. 
The Bacillus is constantly present in the sputum and 
probably in the breath of phthisical patients, and this 
points to the necessity of free ventilation of living and 
sleeping apartments, and disinfection of soiled articles of 
clothing and furniture. The external conditions which, of 
all others, cause a predisposition to consumption are, a 
damp subsoil, causing excess of moisture in the air, and 
the constant breathing of an atmosphere vitiat2d by human 
respiration, It has been asserted that tubercle can be 
propagated from animals to man by the consumption of 
diseased meat, or, in the case of the cow, from the milk of 
a tuberculousanimal. Further proof is required before we 
can accept such an hypothesis, but there is nothing 
improbable in such a mode of conveyance of the disease, 
especially in the case of children with a tubercular 
predisposition. 
Besides the diseases which we 
propagated through the agency of milk—enteric fever, 
scarlet fever, diphtheria, &c, in which the introduction 
of the morbid matter is accidental, the milk serving only 
as a means for its conveyance and perhaps for its growth— 
there is a complaint fairly definite in character, which has 
been attributed to the consumption of the milk of cows 
suffering from foot-and-mouth disease. Here the morbid 
quality is inherent to the milk as taken from the cow, and 
is not due to an accidental introduction. The symptoms 
described in the epidemics recorded are fever, vesicular 
eruptions on the lips and in the throat and mouth, and 
enlargement of the glands of the neck. During the 
prevalence of foot-and-mouth disease, all milk taken by a 
household should be boiled before consumption. In 
view of the many dangers which threaten us through the 
agency of milk, it would perhaps be advisable, especially 
where children are the chief consumers, that t is precau- 
tion should be always adopted ; at least until the sanitary 
authorities in towns have the power of inspecting and 
controlling the farms and dairies in the country from 
which the chief part of the milk-supply is derived. 
The possibility of the transmission of the contagion of 
small-pox for considerable distances, not exceeding one 
mile, through the air, has been warmly supported. ‘There 
are many facts in favour of such a view, and its great 
probability will be seen from the following considerations. 
The contagion is almost undoubtedly a micro-organism of 
the class Bacteria, but as it has not yet been isolated and 
identified, we are unaware if it is capable of spore-forma- 
tion or not. The spores of Bacteria can resist external 
agencies—heat, cold, drying, and antiseptics—to a much 
greater extent than the fully formed organisms, and it is 
probable that those diseases in which the contagion 
remains dormant for long periods are transmitted through 
spores capable of existing for long periods outside the 
body. But in small-pox it is not necessary to rely upon 
spore-formation to support theories of aérial transmission. 
The contagion as given off from the body of the patient is 
inclosed in minute epithelial scales and dry pus accumula- 
tions. Here, protected from the air and from external 
destructive agencies, it may be wafted as a minute dust 
through the air, to descend at considerable distances. That 
the radius of infection from a small-pox hospital as a centre 
does not exceed a mile may be due to the great dilution of 
the contagion as it is diffused through greater distances 
than a mile from its centre of origin, the hospital. The 
observations of Dr. Miquel, at the observatory of Mont- 
souris near aris, have shown the number and variety of 
solid particles which are carried in the air, and the 
immense distances which some of them, as pollen and 
spores, may be presumed to have travelled. An educated 
now know to have been 
