And when we come to the lower animals--even those nearest us in the scale of life--the difficulties are enormously increased. The sense-data are probably much the same, but they are combined in different proportions. Olfactory sensation must, one would suppose, be built into the constructs of the dog and the deer to an extent which we cannot at all realize. And then, as Mr. P. G. Hamerton has well said, we have to take into account the immensity of the ignorance of animals. That ignorance, in combination with perfect perceptual clearness (ignorance and mental clearness are quite compatible) and with inconceivably strong instincts, produces a creature whose mental states we can never accurately understand. I am tempted here to give the instance Mr. Hamerton quotes[GD] in illustration of the ignorance of animals. "The following account of the behaviour of a cow," he says, "gives a glimpse of the real nature of the animal. These long-tailed cows, say Messrs. Huc and Gabet, are so restive and difficult to milk, that to keep them at all quiet the herdsman has to give them a calf to lick meanwhile. But for this device, not a single drop of milk can be obtained from them. One day a Llama herdsman, who lived in the same house as ourselves, came with a long dismal face to announce that his cow had calved during the night, and that, unfortunately, the calf was dying. It died in the course of the day. The Llama forthwith skinned the poor beast and stuffed it with hay. This proceeding surprised us at first, for the Llama had by no means the air of a man likely to give himself the luxury of a cabinet of natural history. When the operation was completed, we found that the hay-calf had neither feet nor head; whereupon it occurred to us that, after all, it was perhaps a pillow that the Llama contemplated. We were in error, but the error was not dissipated till the next morning, when our herdsman went to milk his cow. Seeing him issue forth, the pail in one hand and the hay-calf under the other arm, the fancy occurred to us to follow him. His first proceeding was to put the hay-calf down before the cow. He then turned to milk the cow herself. The mamma at first opened enormous eyes at her beloved infant; by degrees she stooped her head towards it, then smelt at it, sneezed three or four times, and at last proceeded to lick it with the most delightful tenderness. This spectacle grated against our sensibilities; it seemed to us that he who first invented this parody upon one of the most touching incidents in nature must have been a man without a heart. A somewhat burlesque circumstance occurred one day to modify the indignation with which this treachery inspired us. By dint of caressing and licking her little calf, the tender parent one fine morning unripped it. The hay issued from within, and the cow, manifesting not the slightest surprise nor agitation, proceeded tranquilly to devour the unexpected provender."