732 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
from observation that proper clothing, wholesome food, good hygi- 
enic surroundings, avoidance of overfatigue and of depressing psy- 
chic impressions, and that physical care of the body, all contribute 
toward maintaining health as the reverse conditions predispose to 
establishing disease. In seeking the physical basis of this difference 
we must avoid confusing cause with effect. Good hygienic surround- 
ings may act chiefly by excluding the sources of infection rather than 
by enhancing resistance. Yet there is experimental as well as obser- 
vational foundation for the belief in these general influences to affect 
the disposition to acquire or escape infectious disease. Animals 
which are made to fast, to overexercise, are made anemic, are given 
excessive quantities of aleochol and other poisons, or are exposed to 
abnormal cold by shaving of the skin, are more subject to certain 
infections than animals not so treated. If, now, it were found that 
the blood factors governing resistance fluctuated with these influences, 
became smaller and less conspicuous when the influences were bad 
and larger and more efficient when the influences were good, we should 
‘then have established an important concrete fact. 
But the alexinic activity of the blood varies normally within such 
wide limits that only maximal changes could be regarded as signifi- 
cant, and it appears that it is only as the fatal termination of certain 
severe infections are reached—such as experimental anthrax and 
pheumococcus infections, for example—that the alexinic power falls 
greatly or disappears altogether. The determination of phagocytic 
activity outside the body has not thus far been carried out in such 
a manner as to indicate a functional depression which either precedes 
immediately or develops in the course of severe infections; although 
certain infections which take a severe course are characterized by a 
persistent reduction in the number of leucocytes in the circulating 
blood. This latter phenomenon must, however, probably be regarded 
as an effect and not as the cause of the infection. There is, however, 
known at least one example where paralysis of the phagocytes leads 
to a fatal infection under conditions in which the normal phagocytes 
are entirely competent to prevent infection. If to a guinea pig a 
small dose of opium be administered and this is followed by the in- 
jection of a nonlethal quantity of a culture of the cholera bacillus, 
death will ensue because the sensitiveness of the phagocytes to the 
chemical stimulus exerted by the cholera poison has been diminished 
by the narcotic influence of the opium. 
The mean phagocytic value of the blood can, however, be definitely 
raised by certain agencies, that are at the same time and through the 
rise in the number of phagocytes produced, useful in warding off and 
sometimes even in overcoming infection. The means employed to 
bring about an increase of leucocytes, or to establish a hyperleuco- 
cytosis, suffice to maintain the high value for short period relatively 
only, unless the stimulus is frequently repeated. A cold bath, a sun 
