RECIPROCAL INFLUENCE OF ANIMALS. 
637 
French and German beasts, without being themselves affected. 
Heusinger, remarking on this, thinks it very singular, ‘‘ and 
tends to prove that these animals develope a miasma which 
does not act on themselves, but on animals of another 
breed.”* 
The Texan cattle plague may also belong to this type of 
bovine disease. 
The contagious foot-rot of sheep (^pietm contagieux or 
Espagnol of the French, the Spanische Mauenseuche of the 
Germans) is another of these instances in which we have the 
development of a morbific agent in these creatures after leaving 
Spain, and on their arrival in countries where such a disease 
was previously unknown. This malady had not been seen, 
it appears, in France, Italy, or Germany, before the intro¬ 
duction of Merino sheep fom Spain; and from the evidence 
afforded it is believed that no such affection prevails in that 
country. Chabert, who was the first to describe it in 1791, 
and who saw it on the banks of the Gironde, in Bas Medoc, 
and in the Pyrenees, said it was enzootic there. Some time 
afterwards it was observed in Central France, in Piedmont, 
and in England ; in Germany it has been known since 1815 
or 1816. This destructive contagion has frequently appeared 
in the epizootic form, and though it has now domiciled itself 
in these countries, yet the Merino breed out of Spain are 
most predisposed to it. 
It is also worthy of note that one of the most fatal maladies 
to which the ovine race is liable in western countries is the 
louping ill,” or trembling disease,” first described by 
Tessier in 1810, which has only been developed and become 
hereditary since the importation of Merinos.f It was not 
known before that time, and I am not aware that it has been 
observed in Spain. 
Mr. Darwin notices the occurrence of disease after foreign 
sheep had been mixed with home flocks : I have heard it 
stated ill Shropshire, that sheep which have been imported 
from vessels, although themselves in a healthy condition, if 
placed in the same fold with others, frequently produce sick¬ 
ness in the flock.” 
There is much mystery attached to the origin and spread 
of the so-called venereal disease of the horse (maladie vene- 
rienne, syphilis, epizootie chancreuse, typhus venerien, &c.)— 
a disease which does not appear to have as yet manifested 
itself in this country, but, doubtless, like so many which have 
come to us from a foreign source, only awaits importation. 
* ‘ Recherdies de Pathologie Comparee/ vol. i. 
f Richthofen, ‘ Die Traberkrankheit/ p. 19. 
