Most noticeable is this irregularity of respiration in children. We all remember to have seen children fall, and to have remarked with astonishment that, after a shrill scream, they remained still for some time, finally bursting into broken sobs. This is a suspension of respiration. When the sudden pain of a violent blow is felt, the child draws a deep breath with contracted glottis, and emits a sharp cry, then at the height of the inspiration a spasmodic arrest occurs. There are some very nervous children in whom this spasmodic arrest takes place even in slight emotions. I knew a child of this kind, who, one day, because its father had not taken it with him, began to cry brokenly, and suffered an arrest of breath which lasted a minute or longer. The child’s mouth was wide open, he became livid, lips and countenance were purplish, the eyes were half shut and full of tears. The struggle for breath was so great that the child lost its balance and fell, expelled fæces and urine, and then recovered as though nothing had happened. I was told that this took place whenever the child was thwarted. CHAPTER VIII _TREMBLING_ I The old physiologists believed that the mind of brutes only obeyed two stimuli--pain and pleasure, and that all processes of their organism had as aim to avoid the bad and procure the good. Albrecht von Haller combated this opinion in the last century. 'This theory’, he says, 'does not in any way accord with the phenomena. If you consider the movements of an animal during fear, in imminent danger, as having preservation of life for their object, is there anything more absurd than the trembling of the knees and the sudden weakness which befalls it? I am persuaded that all phenomena of fear common to animals are not aimed at the preservation of the timid but rather at their destruction. In order to preserve a just balance it is necessary that the more prolific animals should be destroyed by the less prolific, therefore necessary that those animals destined to be the prey of others should not be able to defend themselves easily’.[15] [15] Haller: _Elementa physiologiæ corporis humani_, tom. v., lib. xvii. § vii. I think Charles Darwin must not have been acquainted with this explanation of trembling, as I am convinced he would otherwise have tried to combat it, or would at least have mentioned it in his writings. He was much too conscientious to ignore an objection made to his theories.