At this point I may refer to a topic of considerable general interest. Animals, in the choice of food for themselves or for their young, are guided by a blind and innate instinct. As I have shown in my second chapter, creatures like the fossorial wasps select only particular species of spiders or insects. Instinct directs them to the kind of food best suited to the wants of their progeny. Bees are attracted by the sweet juices of flowers; the silkworm instinctively devours the leaves of the mulberry and rejects most other plants. In higher animals, instinct plays the chief part in the choice of food. The difficulty of getting rats to eat poisoned food is well known; an instinct warns them of the danger of the material offered to them. In the same way dogs refrain from food that has been poisoned. Every one has seen the minute attention bestowed by a monkey on food before beginning to eat it. It turns over what is offered, smells it carefully, cleans it, and before beginning to eat, subjects it to an examination that seems to us ridiculous. Monkeys often throw away food without even biting it. None the less, in spite of an instinct so highly developed, monkeys poison themselves with all sorts of dangerous substances, even when these exhale a strange odour. I have seen monkeys die poisoned by the phosphorus of matches, or even by iodoform which they had contrived to steal. In the case of man, aberrations of instinct in the choice of food are common. As soon as babies begin to walk, they lay hold of everything and try to eat it. Bits of paper, lumps of sealing-wax, the mucous matter from the nose, all appear to them to be things to eat. Constant guard has to be kept to prevent them from doing themselves an injury. Fruits and berries they cannot resist. Cases of poisoning very naturally are extremely frequent, and as every one must know of instances, I shall mention only a single case. “Messrs. Beadle and Sons, oil manufacturers at Boston, had thrown out, from the door of their establishment, a quantity of castor beans that were decayed and useless. Some children playing in the street mistook the seeds for pistachio nuts, and shared them with their friends. All the children seem to have eaten of them, with the result that more than seventy showed serious symptoms of poisoning.”[84] The consumption of ergotised rye and of maize contaminated with certain leguminous plants (_Lathyrus_) frequently produces epidemics of poisoning without instinct intervening to protect the victims. While the large intestine, acting as an asylum of harmful microbes, is a source of intoxication from within, the aberrant instinct of man leads him to poison himself from without with alcohol and ether, opium and morphia. The widespread results of alcoholism show plainly the prevalent existence in man of a want of harmony between the instinct for choosing food and the instinct of preservation.