228 
HIGHLAND AND AGRICULTURAL SOCIETY. 
have passed without many cases being observed, yet, at intervals of four years, 
influenza seems to give us a specially severe visitation. Thus it is noticed by 
Wilkinson in 1815; by John Field in 1819 and 1823; by Percivall in 1828, 
1832, 1836, 1840, and 1844 (The Veterinarian, 1845.) Most of us remember it 
well in 1848, and still better in 1852. Thus excepting an interval of five years 
in one case (between 1823 and 1828), we can trace its periods of aggravation in 
four-year cycles from 1815 to the present time. 
Causes. — Probably there never was an epidemic, epizootic, or pestilence, that 
affected all the individuals in a community. The plague, cholera, and influenza, 
leave greater or fewer numbers unharmed. Men and animals that become 
affected, are in a state of body different from those that escape. This is called 
predisposition ; the conditions inducing it are called predisposing causes. These 
may not produce any apparent effect so long as they exist alone ; for some special 
excitant, called the exciting cause, may be required for their full development. 
A piece of tinder or gunpowder requires the predispositions of dryness and pecu- 
liar composition, in order to take fire from the action of the kindling or exciting 
spark. Take another illustration ; there is a certain (epidemic) impost called the 
Income-tax; those affected by it, labour under the predisposition — say of £150 
a year income, whilst a man with £149 is not predisposed. Law, impersonated 
in the tax-gatherer, compels the predisposed to pay in proportion to their liability, 
and allows the non-predisposed to escape. Almost all predisposing causes act by 
lowering the general health, and depressing what may be called the vital con- 
servatism of the system. Among the most prominent of these are : over-work, 
with poor feeding; undue exposure to extremes of cold and heat; bad ventilation, 
with its too frequent concomitants, darkness, dampness, and filth. Over- work 
weakens the system directly by exhausting energies beyond their resources. No 
amount of food can compensate for over-reducing labour. Hence, we find in 
many large towns, that the useful, but often hardly-wrought, and imperfectly- 
stabled coach, cab, and omnibus horses, fail largely under influenza. When a 
horse is at ordinary work, the skin becomes raised in temperature ; perspiration 
is excited ; there is an increasingly-rapid passage of blood through the lungs and 
system, in order to maintain animal and organic activity. If the horse be placed 
in a cold or damp stable on coming home, or suddenly exposed to the action of 
cold in any other way, the balance of circulation becomes greatly disturbed. The 
action of cold produces a constringed or contracted state of the skin and its ves- 
sels ; blood is repelled from outward surfaces, and must collect round and within 
internal organs, causing their congestion, a condition but one stage short of 
inflammatory action. Repeat this process once or twice a day, — that, too, in 
winter or spring weather, — then judge from your own feelings what will be the 
result. Many of us can date an attack of illness (possibly of influenza) from 
causes of this kind. To-day, for instance, we are heated with exercise ; we get 
cool by standing in a draught; then comes a shudder without, and a chill within; 
to-morrow we have a sore throat, and oppressed chest. There seems something 
specially irritating in the cold and draught of a spring east, or north-east wind. 
Horses, for instance, are changing, or preparing to change, their coats; the skin 
has commenced an activity, which is arrested or destroyed by the prolonged 
action of cold. When horses are kept in open exposed courts, which, in many 
instances, are damp also, the action of cold, injuriously alternating with the heat 
occasioned by labour, is all the more severely felt. Mr. Proctor, of Liverpool, 
informs me, that influenza is extremely common in draught horses engaged in 
drawing timber from the docks, where they are exposed to draughts of cold air, 
after being kept in a warm stable, or heated by exercise. Mr. Goodwin, Veteri- 
nary Surgeon to the Queen, remarked, during the influenza of 1844-5, that most 
of his affected horses stood on the sides of stables exposed to the north-east. (The 
Veterinarian, 1845, p. 187.) A cold wind blowing directly into a compara- 
tively well-ventilated stable, will often induce coughs and colds in abundance. If 
the stable be close, warm, and damp, the colds will often run on to bronchitis 
and pneumonia, or bad cases of influenza will occur if that epizootic be prevail- 
ing. The animal body is ever taking in material for its support and purification 
in the shape of air. as well as food ; and is as continually separating or voiding 
