Some of Darwin's descriptions of emotional outbursts are among the best portions of his writing; as when he speaks of a mother whose infant has been intentionally injured, "how she starts up with threatening aspect, how her eyes sparkle and her face reddens, how her bosom heaves, nostrils dilate, and heart beats." In describing a mourner when quiescent, he says: "The sufferer sits motionless, or gently rocks to and fro; the circulation becomes languid; respiration is almost forgotten, and deep sighs are drawn. All this reacts on the brain, and prostration soon follows with collapsed muscles and dulled eyes." One of the most striking features of this book is the evidence it affords of Darwin's acuteness and persistence in observation during his travels, and of the excellence of his memory. "I remember that my mules and dogs, brought from a lower and warmer country, after spending a night on the bleak Cordillera, had the hair all over their bodies as erect as under the greatest terror." He noted that Jemmy Button, the Fuegian, blushed when he was quizzed about the care which he took in polishing his shoes, and in otherwise adorning himself; and this fact long after is fitted into the theory of blushing. Guanacoes in South America, when not intending to bite, but merely to spit their offensive saliva from a distance at an intruder, yet retract their ears as a sign of their anger; and Darwin found the hides of several which he shot in Patagonia, deeply scored by teeth marks, in consequence of their battles with each other. A party of natives in Tierra del Fuego endeavoured to explain that their friend, the captain of a sealing vessel, was out of spirits, by pulling down their cheeks with both hands, so as to make their faces as long as possible; and the fact is treasured till it comes in to illustrate the lengthening of features under depression. As if he foreknew that he should want the fact forty years later, he inquired of Jemmy Button whether kissing was practised by his people, and learnt that it was unknown to them. "I remember," he says, "being struck whilst travelling in parts of South America, which were dangerous from the presence of Indians, how incessantly--yet as it appeared, unconsciously--the half-wild Gauchos closely scanned the whole horizon." "In Tierra del Fuego, a native touched with his finger some cold preserved meat which I was eating at our bivouac, and plainly showed utter disgust at its softness; whilst I felt utter disgust at my food being touched by a naked savage, though his hands did not appear dirty." And this illustrates the primary meaning of disgust--anything offensive to the taste.