Contagiousness of Leprosy. 279
respective families lived together. In many instances no
special notice had been taken of this fact, and all these have
been disregarded unless a case of leprosy occurred amongst
the children. Now, no doubt, as in many of the cases left out
on account of insufficient details there has been no separation
or segregation of the leper, this table will over-rate the chances
of a possible contagion rather than under-estimate it. It will
be seen that about 5 per cent. of the persons living in daily
intercourse with lepers under the same roof at one time or
other developed the disease. A number of children have been
left out of consideration because they died as infants or while
very young. This has been done in order to give the argu-
ment in favour of contagion every possible advantage, for surely,
where contagion as such is discussed, age need hardly be consi-
dered. If a disease be contagious it should be so at any age.
But if it is necessary to assume a long incubation period, as many
writers do, which sometimes extends through infancy and child-
hood, until what is called the probable age of attack is reached,
this is surely an unjustifiable extension of the term contagion,
or a practical denial of the influence of contagion by a reduction
to an absurdity. Again, in some cases entered in the table,
the diagnosis of leprosy was extremely doubtful, and in one
case the child contracted the disease at the same time as the
father. Thus by allowing the validity of these cases a further
advantage is allowed to the hypothesis of contagion. And yet
in only 5 per cent. of the cases could a possible influence be
assumed.
But the ratio obtained from this table of course cannot be
taken to represent the actually existing chances of infection.
For from among the total community coming into contact with
lepers, only a few have been selected. Moreover all other
causes, such as endemicity, or a de novo origin of the disease,
have been altogether disregarded. However, assuming, for
argument's sake, that all the above cases are genuine instances
of contagion, and that the spread of leprosy depends on this