460 Philippine Journal of Science 1919 
their feeces were examined every other day and found con- 
tinuously positive. No. 8617, after having been a carrier for 
seventeen days, became ill with frank cholera; No. 12765 was 
a carrier for sixteen days before he came down with the disease, 
and No. 30351, for eighteen days; the last-mentioned individual 
died of the disease. 
The question naturally arises: What is the cause of develop- 
ment of cholera in carriers? In so far as our present knowl- 
edge of the subject goes this is an unanswerable question. For 
want of anything more definite, it may be said in a general ~ 
way that a lowering of vital resistance permits invasion. If 
this hypothesis be true, then we can easily understand how a 
carrier may become a victim to the disease at this time. But 
not everything is explained even by the theory of lowered vital 
resistance; it is still an open question. Some workers are in- 
clined to believe that the organism itself, as occurring in persons 
of carriers, fluctuates in virulence; but this belief is scarcely 
tenable, and may be dismissed with scant discussion. However, 
it may be that the cholera vibrio requires passage through an 
intermediate human host before causing symptoms. My own 
observations are to the effect that the vibrios isolated from a 
carrier, either while living or after death, behave in exactly 
the same manner as do those obtained from a frank cholera 
case; there is absolutely no difference. 
Once a cholera carrier, how long does this condition exist? 
This is a question of the greatest importance for the health 
officer. The answer can only be obtained from the laboratory, 
and unfortunately we are unable to answer definitely. We know 
that in the typhoid carrier the period of infection lasts for 
years, very likely for the life of the individual. Some obser- 
vations made on prisoners in Bilibid would seem to indicate that 
very likely the cholera-carrier state may be of indefinite duration. 
Prisoner 8841 was positive on September 12, 1914, had seven 
negative examinations at intervals of four days, was released 
from quarantine, and was not reéxamined until July 15, 1916, 
when he was positive again; negative until September 10, when 
he was once more positive; negative until December 31; posi- 
tive again January 13 and 18, 1917; negative on January 24, 
but a nonagglutinable vibrio was isolated; January 25, 27, 30, 
and February 3, respectively, a nonagglutinable vibrio was 
isolated; February 7 he was once more positive; February 10, 
15, 17, 20, 22, 27, and March 1, respectively, a nonagglutinating 
