[Reprint from the St. Louis Courier of Medicine, March, 1885-1 
ON THE COURSE AND DESTINY OF POPULA- 
TION INFECTIONS. 
By Geo. Homan, M. D., St. Louis. 
[Bead before the St. Louis Medico-Chirurgical Society, January 27,1885.] 
IN his general observations on the course and causes of the 
plague in the fourteenth century, Hecker1 says: 
“That Omnipotence which has called the world with all its liv- 
ing creatures into one animated being, especially reveals himself 
in the desolation of great pestilences. The powers of creation 
come into violent collision; the sultry dryness of the atmosphere; 
the subterraneous thunders; the mist of overflowing waters, are 
the harbingers of destruction. Nature is not satisfied with the 
ordinary alternations of life and death, and the destroying angel 
waves over man and beast his flaming sword. 
“Were it in any degree within the power of human research to 
draw up, in a vivid and connected form, an historical sketch of 
such mighty events after the manner of the historians of wars 
and battles, and the migrations of nations, we might then arrive 
at clear views * * and the ways of Providence would be 
1. Epidemics of the Middle Ages, Sydenham Society, 1844. 2 
more plainly discernible. * * * All this,- however, takes 
place upon a much grander scale than through the ordinary vi- 
cissitudes of war and peace, or the rise and fall of empires, be- 
cause the powers of nature themselves produce plagues, and 
subjugate the human will, which in the contentions of nations 
alone predominates. ” 
The consideration of the infectious and spreading ills that 
have ever more or less actively beset the life of collective man 
has been a theme of absorbing interest from times most dim 
and ancient; and the pages of written speech contain no more 
moving and graphic narratives than those wherein are described 
and set forth the advent, the agony and fatalities of destroying 
epidemics amidst sparse or thronging populations. The descent 
of the plague upon a supine or preoccupied people was likened 
to the falling of rain from heaven; and the prophecy concerning 
a numerous people that “their dead bodies shall lie in the 
streets of the great city,” expressed the extremest mortal ill that 
could be visited upon man by sweeping and pitiless infection. 
Or, again, ‘ ‘To the great city that thought it would sit as a lady 
forever, there came in one day widowhood and loss of 
children,” are the striking words that tell of the self-complacent 
negligence, and the surprise and swift desolation of an ancient 
and opulent metropolis. 
Not decimation merely, but depopulation and desolation more 
than once in earlier times marked the course and termination of 
pestilential sojourns over inhabited areas of very considerable 
extent. The movements and migrations of population were 
then but slow as compared with present times—the losses sus- 
tained in human life being made good with difficulty, as the 
mention or memory of the horrors and bitter experiences of 
such scenes and occurrences, and to which were commonly added 
the miseries of extended famine, served to retard and make du- 
bious speedy and efficient recuperation through immigration or 
natural increase. 
That the violence and vitality of human infections, and the via 
bility of epidemical disease was greater then than now is conclu 
sively shown by ample and competent testimony reaching back 
through many centuries; and the specific agencies whereby they 3 
operated are now so weakened, comparatively—unless specially 
circumstanced—that epidemiology and pathology scarcely 
recognize to-day in the wasted and fading semblances of certain 
diseases the dreaded instrumentalities that once were armed 
with power to scourge and slay unhindered throughout cities and 
provinces, and even continents and hemispheres entire. 
The histories alike of medicine and mankind present the in- 
structive spectacle of diseases dead or overthrown, and wasted 
and expiring infections; and nothing can more impressively 
convey the lesson of the changes wrought by time and prevail- 
ing associated influences upon types and forms of life than this 
most certain and salient truth. 
The beginning, duration and ending of infections depend 
clearly upon physical influences, and their variations and move- 
ments, however accidental, phenomenal or erratic they may 
seem, are yet controlled in orderly sequence by determinate 
laws that hold equable sway throughout all animate nature. 
Deriving their impetus and power to harm from the minutise of 
quickened organic nature, the study of the fauna and flora of 
microscopic life becomes at once a subject of deep and absorb- 
ing interest; for, by unfailing natural law it seems ordained that 
in their career the lowest shall be the life dependent or adjunct 
of the highest—that the humblest link in the living chain shall 
surely touch and unite with the most exalted to complete the 
circle of animate existence. The life procession of these plastic 
and protoplastic forms and phases ot organized matter is con- 
joined with that of man, within whose vital economy they find 
their appointed range, sustenance or abode. There the decrees 
of their being are fulfilled, and there they round out and justify 
the mission of their existence. Their design, domain and des- 
tiny, as merely abstract subjects of study, are inviting alike to 
pathologist, naturalist and physiologist; while their ani- 
mus, their energies and capacities as causes of far-reaching 
movements hurtful to the health, or fatal to the life of man pos- 
sess a personal and immediate interest to every living human 
being. 
The observant, shrewd good sense of mankind divined the 
living, material basis on which infections rest, and from whence 4 
they derive their hurtful powers,long before science accepted this 
belief as fact, and before any perfect demonstration of its truth 
was possible; and this conclusion was reflected in the every day 
language of the people, “nests and seeds of disease,” “breeding 
places of infection,” “nurseries of fever,” “hot beds of pestil- 
ence,” “plague spots,” and like phrases all in common use, ex- 
pressed the general conviction that plagues and pestilences, 
domestic and foreign, had their origin in and derived their ac- 
tivity from living forms of matter that were quick to respond 
to exciting and favoring local influences. 
Why the resources of disease should fail and infections show 
a declining power is pertinent to the present purpose, and 
while the subject is too vast for a complete exposition of the 
process to be attempted, and, indeed, may as yet be impossible, 
still some note taken of the workings and mutations of nature 
in analogous and collateral, but more openly declared • direc- 
tions, may serve to throw some light on this, as yet, somewThat 
obscure subject—only the briefest reference, however, to a few 
of the leading facts in this connection being here possible. 
It being granted that epidemic maladies have their essential 
and influential sources in the bodily forms and entities of 
microscopic life, and that these in their continuance through 
successive generations, and the transmission of their fundamen- 
tal qualities of group, species or breed, are influenced, shaped 
and determined by their treatment and environment, then the 
only further admission required is that they are likewise subject 
to the operation of a general law observed throughout nature, 
and which is not invalidated by application to even the lowest 
forms of life. 
Absolute dominion of physical agents over organic forms is 
declared by high authority to be the fundamental principle in 
all the science of organization; and that living forms in the 
manner of their development depend altogether on the circum- 
stances to which they are exposed. So long as these are the 
same the resulting form will be the same, and so soon as these 
circumstances differ, the resulting form differs too. With dif- 
ference in form come necessarily changes in function, aptitude 
and in parental or hereditary entailments. 5 
The experience had in the domestication, cultivation and rais- 
ing of animals and plants shows in a striking manner the effect 
of careful selection, breeding, surroundings, etc., in developing 
desirable and overcoming objectionable features or qualities in 
breed or species subjected to. such treatment. Careful observa- 
tion and experiment show that this holds equally good with the 
lower forms of life, and that in feature and function the indi- 
viduals thereof breed as true to type as the higher ones, and 
that successive generations are modified by the conditions in 
which they are placed, abundant nourishment causing rapid and 
efficient reproduction, while starvation will restrict the increase 
as well as weaken the vigor of the brood. 
The quality of generative prepotency, or the power to 
closely transmit to descendants ancestral characteristics, is 
marked in'beasts and plants in a state of nature, being especially 
so in wild animals; but it is capable of acquisition in domesti- 
cated strains, and may be fixed by long continued breeding to a 
given desired type; and when attained, the esteemed qualities 
are perpetuated in the offspring with occasional flaws, reversions, 
and variations through continuous successive generations. Or, 
a prepotent individual may unexpectedly appear of unusual ex- 
cellence—or the opposite—in many points, whose descendents 
will be strongly impressed with his distinguishing desirable or 
ignoble qualities. Growers and breeders of stock have long 
more or less perfectly understood and taken advantage of the 
opportunities afforded by the laws of heredity and prepotency, 
and have shaped and modified in strain and breed the charac- 
ters and features of their flocks and herds by the selection of 
progenitors with a careful reference to the securing of desirable 
qualities of form, fibre, fleece, flesh, etc. The fierce, the wild, 
the coarse, the weak or the noxious instincts and characteristics 
,of ancestral types have thus, by judicious selection and intelli- 
gent care, been eliminated, and milder, useful and profitable 
qualities have been impressed instead upon their progeny. 
But, marked as acquired prepotency may be, it may yet dis- 
appear and be lost as a result of causes operative either from 
within or without, close breeding even, and in-and-in breeding 
certainly, sometimes resulting in its extinguishment;' fertility 6 
between relations ceasing, although the existing individuals 
may be in appearance the most perfect of their kind. As these 
artificial types, however stable they may seen, may be lost 
through lack of care or otherwise, so the untamed or untamable 
aboriginal and most markedly prepotent species may be forced 
to extinction by adverse conditions as of food and climate, or 
by the relentless pursuit of natural enemies. 
In former times the unsparing vigor and wide extending 
power of diseases which still claim recognition amounted to in- 
herent prepotency of their organic causes, there being a swift- 
ness and deadliness marking their course unknown even in the 
worst epidemic of modern times among civilized peoples; and 
a review of the history and course of population pestilences, 
with due note taken of the progress and influence upon them of 
time and civilization, shows not a few resemblances between 
the manifest lessening of their destroying energies, with the at- 
tendant exhaustion or subjection of their living causes, and the 
results observed in the domestication of species and individuals 
derived from the animal or vegetable kingdoms of wild or primi- 
tive nature. 
The virtual if not actual extinction of some of the more vio- 
lent and fatal forms of human disease, together with the grad- 
ual visible weakening of others, clearly shows the past and 
present trend of population poisons, and the value and efficiency 
of measures intelligently designed and applied for the protec- 
tion of population health. 
In a public health sense the measure of civilization in a given 
community is the degree of elevation in the personal and do- 
mestic habits and environment of each individual; and, more 
especially, that of the aggregate personnel of the indigent, the 
negligent and the toiling classes, for it is in the midst of these 
that infections most commonly find all the requisites of prolific 
and typical development. The advance of civilization is marked 
by a growing regard for the moral and physical welfare of these 
classes, and in proportion as their housing, food, drink, clothing 
and the ultimate details of their domestic life are bettered, in 
just that degree is pestilence forestalled and denied the conditions 
amid&t which it most readily feeds and breeds. The struggle of mankind along the path of enlightenment 
and progress has been marked by a corresponding decline in the 
power of disease—a wide and very general slaughter having 
been the rule rather than the exception in earlier times, while 
now sweeping epidemics are exceptional, save among the semi- 
civilized or savage, and their mortality is comparatively slight. 
The reasonable explanation of this may be found, it is be- 
lieved, in the fact that mankind, through the arts, aids and ap- 
pliances of civilization has, unconsciously often and usually in a 
blind, uncertain, imperfect way, produced effects upon the ac- 
tive causes of his peculiar infections analogous to those observed 
in the taming and subjection of original forms of animal and 
vegetable life. For, as these minute living bodies or energies 
are the outcome and expression of special determining condi- 
tions, then, agreeably to the laws of evolution, when the condi- 
tions which gave them birth and maintained their identities are 
withdrawn or altered, the character of the off- 
spring changes too; and if, by reason of favoring circum- 
stances of soil, season and environment, these in their begetting 
and growth are certain of purpose and ample in power to fa- 
tally touch the life of collective man, then plainly his first in- 
stinct and most immediate and pressing concern would be to 
discover and apply every measure that is capable of attacking, 
deranging or removing these specific and dangerous condi- 
tions. 
To systematically and continually deny to morbid organisms 
all favoring circumstances amidst human populations, to thwart 
their purpose and disarm their power, to cut them off from the 
means of living and starve them to extinction, or to breed such 
types, benign in character, as will supersede and protect against 
the [original and injurious ones, are now the conscious and 
avowed aims of the highest human intelligence and civiliza- 
tion. 
As the plagues of antiquity are now scarcely known save in 
history, so the destroying epidemics of the middle ages, such as 
leprosy, syphilis, measles, typhus and small-pox, have yielded 
their fatal energies, and now retain scarcely a tithe of their for 
mer aggressive malignity amongst civilized peoples. 8 
An accidental clue, laboriously followed up and skillfully de- 
veloped, led to the discovery of protective vaccination, and the 
resulting conquest of a disease which, previously, was more dis- 
astrous to human kind through death and disfigurement, than 
all the wars waged by man during the same period of 
time—excessive as even such losses were. Ultimately and in 
effect the vaccine culture and process is simply the do- 
mestication and close breeding of a certain dis- 
ease entity, as is practiced upon animals and plants, 
reversions to the original type being observed as with them, 
while in-and-in breeding results in infertility, the acquired pre- 
potency of the benign organism being thus weakened or lost; 
and, without taking account of susceptibility, soil or medium 
of culture and other factors in the case, hence follow the abor- 
tive, atypical or negative vaccinations not infrequently ob- 
served. 
Although scurvy may not properly be classed with infections, 
still its chief factors are bad air, bad food and bad surroundings; 
and while scarcely known now was, prior to the two generations 
past, for centuries present in almost every ship, jail, workhouse 
and hospital and in many private dwellings throughout the civ- 
ilized world. By statistics, whose accuracy may not be ques- 
tioned, it is shown that during the last two centuries the deaths 
from scurvy in the British Royal Navy exceeded in number all 
the fatalities from battle and wreck and other casualties of sea- 
faring life; and this, too, in times when every maritime nation 
that could sail a ship or fire a gun was sooner or later at war 
with this power, and when sea-fights and blood-shed were 
events of the most common occurrence. Such was the havoc 
wrought by this one dreaded affliction, a death from which is 
now unknown, and which now finds scarcely a place of lodgment 
in all the world. And this result was brought about simply by 
increased enlightenment as to its causes, and a little practical 
care and forethought in the way of prevention. 
Typhus was the close companion of scurvy, and like it has faded 
from sight as a palpable factor of mortality. The plague.1 with 
1. Ilecker says that'in'the course of the Black Death in Europe, 9 
all that the term comprised in variety of morbid features, has 
also passed away. Measles, which two hundred years ago was 
as fatal as any disease known to present times, has been brought 
to a type so mild as often to be scarcely recognized. Leprosy, 
which during the middle ages and from earliest times claimed 
kings and beggars alike among its victims, now reduced to a 
shadow of its former self, lingers precariously in a few of the 
by-places of the world. Syphilis retains none of the malignity 
that once marked its course, a death from its sequelae even being 
now infrequent. 
Clearly the age of population infections is passing away; for, 
though certain spreading diseases still survive to swell the mor- 
tality reports, yet their power is visibly decayed and surely wan- 
chiefly during the years between 1347 and 1351 there was a mortality 
from this cause alone of nearly 25,000.000 persons, this estimate being 
the lowest made by trustworthy authorities of that age, and was the 
result of a careful examination of all attainable documentary evidence 
of the period named made by the author mentioned. 
The ratio of mortality to population was the same as if 15.000.000 
deaths from cholera should occur in this country during the next three 
years. A report made by order of Pope Clement showed 23,840,000 
deaths from the plague in Asia, exclusive of China. Many districts and 
cities were depopulated, and often only one person in ten was left alive. 
Italy and France were terribly scourged, while Germany lost more than 
1,200,000 lives in three years, the visitation being regarded as a rather 
light one, although during the entire course of the plague, the Francis- 
can friars throughout Germany alone reported a loss in membership of 
124,434, while the Minorities in Italy lost 30,000. 
Such was the deadliness of the infection that many died without a 
visible symptc and vast numbers within twenty-four or forty-eight 
hours of attack. Unburied corpses lay in the fields, roads, streets and 
houses, and ship were often seen driving about in the Mediterranean 
and North Seas and drifting ashore with only the dead on board, the 
crews having perished to the last man. 
In England 100,000 deaths at least occurred in London, and in Nor- 
wich 51,000. In France, Paris lost 50,000, Avignon 60,000 and Mar- 
seilles 16,000 in one month. In Italy, Venice lost 100,000, or three- 
fourths of her population, and Padua two-thirds of hers. Florence lost 
60,000 and Siena 70,000. At the height of the disease in Vienna 1,200 
died daily, while in the Levant, Aleppo lost 500 per day, Gaza 22,000 in 
six weeks, and during its deadliest prevalence in Cairo a trustworthy 
observer estimated the daily death rate at from 10,000 to 15,000. 10 
ing. The tendencies of the times in the way of perfected drain 
age, which means cleanness and dryness of soils, cities and houses 
—every movement to get pure water in a more abundant sup- 
every effort to dispel darkness and damp by the letting in 
of sunlight and fresh air, every attempt to blight or poison by 
chemical means the living agents of infection, everything done 
to make cheaper and better necessary articles of food, drink or 
wear—in a word, every measure and endeavor in this direction 
tends to destroy the prepotency of plague breeders, and is a blow 
aimed at the sources and lives of organisms from which come 
not only the sweeping infections that may traverse the 
world, but also of the creeping infections that wait 
on uuclean surgery and midwifery; and which still inhabit 
badly kept prisons, hospitals, tenements, sleeping rooms, clos- 
ets, basements and the like places. 
Any hypothesis that regards infectious diseases as being other 
than the outcome and evidence of stir and activity among min- 
iature, definite forms of life and being, fails to account for and 
explain all the phenomena observed; but with increasing knowl- 
edge man has the assurance of ability to control fully the causes 
and circumstances of their generation and development. 
The manifest course of infections coming from without, and 
which tend to spread wddely and fatally, is in the direction of 
gradual and sure mitigation, in this respect keeping step with 
the advance of true enlightenment, and their destiny then is nat- 
urally toward final extinction; and, provided that the condi- 
tions that brought them into being and enabled them to live do 
not recur through negligence, and, provided further that new 
forms of spreading disease do not arise to take their place, then 
mankind in the future will have little to fear of evils to health 
save from those which are entirely home-bred, and which tend 
to domestication within his own doors. 
It being evident that a number of the specific causes from 
which proceed epidemical impulses have been and now are 
greatly curtailed in their power for harm, and that others again 
have become to all purposes extinct, then this result and the 
manner and means by which such saving in human health and 
life was brought about becomes a matter ot interest and congrat- 11 
ulation to all; and, if the progress of time and civilization lias 
shown, and still shows, a steadily increasing avoidance, removal 
or mastery of the causes of danger to human health, then this 
fact and deliverance constitute a triumph of human effort and 
intelligence over physical evil, and it may be justly claimed 
that men do hold largely in their hands the issues of life and 
death to the great body of their fellow men. 
And the increasing consciousness of this knowledge and power, 
together writh the growing general enlightenment upon public 
health matters, have caused mankind to depend less upon Provi- 
dence than on themselves for protection; and the disposition to 
do this is becoming so strong that it is not unlikely in the near 
future that it will become a settled principle of law, and be 
made a part of such by statutory enactment, that municipali- 
ties shall be held responsible in actual if not exemplary dam- 
ages for losses to business interests directly caused by epidemics 
of avoidable diseases, and which diseases were introduced or per- 
mitted to spread by reason of ignorance or lack of diligence on 
the part of the officials or agents of such municipality in refusing 
or neglecting to take the necessary plain, effective and proper 
steps to prevent the introduction and stop the spread of such 
disturbing or fatal epidemics.