rather ashamed of himself for having called the cat the dog, he took up the cat in his arms and looked at her very attentively for some time stroking her all the while; and in this way he associated the impression derived from the touch, and made himself master (so to speak) of the whole idea of the animal. He then put the cat down, saying: "Now, puss, I shall know you another time."--CARPENTER.] 50. Why can a skillful surgeon determinate the condition of the brain and other internal organs by examining the interior of the eye? [Footnote: This is done by means of an instrument called the ophthalmoscope. Light is thrown into the eye with a concave mirror, and the interior of the organ examined with a lens.] 51. Is there any truth in the idea that the image of the murderer can be seen in the eye of the dead victim? 52. What is the length of the optic nerve? _Ans_. About three fourths of an inch. 53. Why does an injury to one eye generally affect the other eye? _Ans_. The optic nerves give off no branches in passing from their origin in two ganglia situated between the cerebrum and the cerebellum, and their termination in the eyeballs; but, in the middle of their course, they _decussate_, or unite in one mass. The fibers of the two nerves here pass from side to side, and intermingle. The two ganglia are also united directly by fibers. Thus the eyes are not really separate organs of sight, but a kind of double organ to perform, a single function. IX. HEALTH AND DISEASE.--DEATH AND DECAY. "Health is the vital principle of bliss." THOMSON. "There are three wicks to the lamp of a man's life: brain, blood, and breath. Press the brain a little, its light goes out, followed by both the others. Stop the heart a minute, and out go all three of the wicks. Choke the air out of the lungs, and presently the fluid ceases to supply the other centers of flame, and all is soon stagnation, cold, and darkness." O. W. HOLMES. "Calmly he looked on either Life, and here Saw nothing to regret, or there to fear; From Nature's temp'rate feast rose satisfy'd, Thank'd Heaven that he had lived, and that he died." POPE. HEALTH AND DISEASE.--DEATH AND DECAY. VALUE OF HEALTH.--The body is the instrument which the mind uses. If it be dulled or nicked, the effect of the best labor will be impaired. The grandest gifts of mind or fortune are comparatively valueless unless there be a healthy body to use and enjoy them. The beggar, sturdy and brave with his outdoor life, is really happier than the rich man in his palace with the gout to twinge him amid his pleasures. The day has gone by when delicacy is considered an element of beauty. Weakness is timid and irresolute; strength is full of force and energy. Weakness walks or creeps; strength speeds the race, wins the goal, and rejoices in the victory.