GENERATION OF POISONS. 
405 
We need not, however, be astonished at this singular pro¬ 
perty ; for why should not certain morbid principles be in this 
manner rejected from all the secretions in which the normal 
conditions remain unimpaired? The same thing appears to 
take place with respect to the contagious pneumonia of 
horned cattle. We are aware that volatile emanations trans¬ 
mit the morbid principle; but experiments have been tried 
(in Belgium) for the purpose of inoculating it directly to 
animals, as a preservative against the disease. Something 
similar to the process of inoculation in the smallpox was 
expected to result from this; it was then discovered that 
neither the animal’s blood, nor any of the fluids of the eco¬ 
nomy, was endowed with the property of propagating the 
complaint. It appears to have chosen the lung for its exclu¬ 
sive seat; and the liquids therein contained, pus, lymph, etc., 
are alone endowed with the property of transmitting the 
complaint. The intense local inflammation which follows 
the operation sufficiently testifies to the noxious properties 
of this virus; and when, in order not to spoil the animal’s 
flesh, the tail is selected as the point where inoculation is to 
be performed, the subsequent inflammation frequently causes 
it to mortify. 
Here, then, we have another virus which exclusively re¬ 
sides in the tissue of the lungs, and is not found in the blood 
at large; but even in the normal state a great many sub¬ 
stances are found in various tissues, which do not exist in 
this fluid. Thus, muscular flesh contains a large amount of 
salts of potash, while scarcely any trace of them is found in 
the blood; in a word, the various bodies found in different 
parts of the economy are not invariably represented in the 
torrent of the circulation. 
The history of specific diseases offers, therefore, nothing 
which cannot rationally be explained; it now remains for us 
to discover the physiological process by which a virus may be 
originated. Nothing is easier than to produce putrid affec¬ 
tions in sound animals. Thus, when transfusion is performed 
under the ordinary conditions—when the blood is conveyed 
directly from one animal into the veins of another—no acci¬ 
dents whatever are produced; but if the blood is allowed to 
remain for a short space of time in contact with the atmo¬ 
sphere, and if the serum is then injected into the vessels, all 
the symptoms of putrid resorption are observed, and the 
animals die after exhibiting all the characteristic symptoms 
of putrid infection. 
The blood is therefore capable of acquiring toxic properties 
without the intervention of any foreign principle, merely 
