But the more I consider the point the more am I inclined to regard these two instincts as separate in their origin, although I retain the belief that cattle and horses and several wild animals are violently excited by the smell of blood for the reason just given--namely, their inherited memory associates the smell of blood with the presence among them of some powerful enemy that threatens their life. To this point I shall return when dealing with the last and most painful of the instincts I am considering.
The following incident will show how violently this blood passion sometimes affects cattle, when they are permitted to exist in a half-wild condition, as on the pampas. I was out with my gun one day, a few miles from home, when I came across a patch on the ground where the grass was pressed or trodden down and stained with blood. I concluded that some thievish gauchos had slaughtered a fat cow there on the previous night, and, to avoid detection, had somehow managed to carry the whole of it away on their horses. As I walked on, a herd of cattle, numbering about three hundred, appeared moving slowly on towards a small stream a mile away; they were travelling in a thin long line, and would pass the blood-stained spot at a distance of seven to eight hundred yards, but the wind from it would blow across their track. When the tainted wind struck the leaders of the herd they instantly stood still, raising their heads, then broke out into loud excited bellowings; and finally turning they started off at a fast trot, following up the scent in a straight line, until they arrived at the place where one of their kind had met its death. The contagion spread, and before long all the cattle were congregated on the fatal spot, and began moving round in a dense mass, bellowing continually.
It may be remarked here that the animal has a peculiar language on occasions like this; it emits a succession of short bellowing cries, like excited exclamations, followed by a very loud cry, alternately sinking into a hoarse murmur, and rising to a kind of scream that grates harshly on the sense. Of the ordinary "cow-music" I am a great admirer, and take as much pleasure in it as in the cries and melody of birds and the sound of the wind in trees; but this performance of cattle excited by the smell of blood is most distressing to hear.