284 
CONTAGION AND MIASMS. 
The horse may have two kinds of itch : the first of which 
is due to the presence of the acarian parasite proper to 
herbivora, and long known, which cannot trace furrows, live 
on the skin of man, or transmit the contagion to him ; the 
second, due to the presence of an acarus identical with that 
of carnivora, capable of tracing furrows, of transmitting psora, 
and of which no one has hitherto suspected the existence. This 
transmissible disease is as different in the whole of its 
symptoms from that which cannot be communicated as the 
parasites which cause them to differ from each other. — Comptes 
Rendus, No. 5, Feb. 1856. 
ON CONTAGION AND MIASMS. 
The morbific action of matters of contagion and miasms 
are ascribed by Liebig to their operation as ferments. It is 
known that during putrefaction, at a stage prior to any fetid 
gas being evolved, a peculiar organic substance is generated, 
possessed of intensely poisonous properties, and that the 
blood of persons who have died from its effects is found to 
be quite disorganized and irritating when applied to -wounds. 
“ In order/’ says Liebig, “ to attain a clear conception of the 
mode of action of these bodies, it is necessary to call to mind 
the cause on which the phenomena of fermentation, decay, 
and putrefaction depend. This cause may be expressed by 
the following law, long since proposed by La Place and 
Berthollet, (( a molecule set in motion by any poiver can impart 
its oivn motion to another molecule , with which it may be in 
contact A body in the act of decomposition, added to a 
mixed fluid in which its constituents are contained, can re- 
produce itself in that fluid exactly in the same manner as 
new yeast is produced when yeast is added to bodies con- 
taining gluten. The small quantity of diseased organic matter 
originally introduced into the system by absorption, acts as a 
ferment, reproduces itself in the mass of blood until this 
becomes unfitted for the performance of its functions, and 
the animal dies. The fatal effects of eating bad sausages are 
ascribed by Liebig to this peculiar action. Several hundred 
cases are known in which death has occurred from the use of 
this kind of food. In Wurtemburg, the sausages are prepared 
from very various materials, such as blood, liver, bacon, 
brains, milk, meal, and bread, mixed together with salt and 
spices ; the mixture is put into bladders or intestines, and, 
after being boiled, is smoked. When well prepared they 
may be preserved for months, and furnish a nourishing and 
