644 CONTAGION AND INFECTION. 
the skin overlying the part, and ulcerating farcy-buds are 
formed. On the surface of the more vascular mucous mem- 
branes effusions of tubercular matter are also poured out ; 
these take on an unhealthy inflammation, and degenerate 
into chancrous ulcers, which may generally be seen on 
the mucous membrane of the nostrils in most bad cases of 
glan ders. 
These are the most common scrofulous diseases of horses ; 
but an animal of the scrofulous diathesis, besides being 
specially subject to these, is little able to withstand ordinary 
morbific causes, and hence is also unusually liable to many 
ordinary diseases ; in such a subject, too, disease is very apt 
to be severe and complicated, and to be acted on tardily and 
imperfectly by all remedies. 
ON CONTAGION AND INFECTION IN RELATION TO 
EPIDEMIC DISEASE. 
In a Paper Read at the Epidemiological Society. 
Dr. M‘William endeavoured to illustrate the confusion 
and misunderstanding which at present existed on the subject 
of contagion and infection, arising from the arbitrary and 
uncertain signification attached to these words. The chief 
sources of error he traced to the transmutation of their 
meaning ; that at one time they are employed to denote a 
cause, and at another an effect ; that they are used to desig- 
nate the agent or poison which causes a disease, and the 
contamination or effect of the poison. To obviate this 
source of error, he suggested, that as contagion was derived 
from contagio , which signified the act of contamination, and 
infection from infectio , the act of infecting ; they should be 
limited to define the act or effect. That as the word contagium 
is synonymous with miasma or poison — viz., that which 
ence consisting chiefly in a diminution of the red corpuscules, and a proportional 
increase of the fibrine and albumen : — 
Blood of Healthy Horse. Blood of Glanderous Horse. 
A. B. 
Water . 
804-75 
842- 
859* 
Fibrine , 
2-41 
6-60 
8-7 
Blood corpuscules . 
11713 
68-20 
44*20 
Fat 
Albumen 
1-13 ) 
67-85 S 
76-70 
82-27 
Soluble salts . 
6-82 
6-50 
5-38 
Simon's Animal Chemistry , by Dr. Day, vol. i, pp. 346-7 
