the impression. This state may last for a considerable time.
129.
The aëronauts, particularly Zambeccari and his companions, relate that they saw the moon blood-red at the highest elevation. As they had ascended above the vapours of the earth, through which we see the moon and sun naturally of such a colour, it may be suspected that this appearance may be classed with the pathological colours. The senses, namely, may be so influenced by an unusual state, that the whole nervous system, and particularly the retina, may sink into a kind of inertness and inexcitability. Hence it is not impossible that the moon might act as a very subdued light, and thus produce the impression of the red colour. The sun even appeared blood-red to the aëronauts of Hamburgh.
If those who are at some elevation in a balloon scarcely hear each other speak, may not this, too, be attributed to the inexcitable state of the nerves as well as to the thinness of the air?
130.
Objects are often seen by sick persons in variegated colours. Boyle relates an instance of a lady, who, after a fall by which an eye was bruised, saw all objects, but especially white objects, glittering in colours, even to an intolerable degree.
131.
Physicians give the name of "Chrupsia" to an affection of the sight, occurring in typhoid maladies. In these cases the patients state that they see the boundaries of objects coloured where light and dark meet. A change probably takes place in the humours of the eye, through which