THE NERVOUS SYSTEM AND ORGANS OF SENSE 411 



images of lines transverse to the former are distinct. Many nervous 

 troubles, especially headaches, may be due to eye strain. We had better 

 have our eyes examined from time to time, especially if we have head- 

 aches. 



How we See. Suppose an object be held in front of the eye ; rays 

 of light pass from every part of the object and are brought to a focus on 

 the retina by means of the transparent lens. You can form an object in 

 the same manner by using a reading glass, a box with a hole in one end, and 

 a piece of white paper. Notice that the image is inverted. The same is 

 true of the image on the retina. By means of this image thrown on the 

 sensory layer, the rod and cone cells of the retina are stimulated and the 

 image is transmitted to the forebrain. We must remember that the optic 

 nerve crosses under the brain so that images formed in the right eye are 

 received by the left half of the forebrain, and vice versa. 



The Paralyzing Effects of Alcohol on the Nervous System. Alcohol 

 has the effect of temporarily paralyzing the nerve centers. The first effect 

 is that of exhilaration. A man may do more work for a time under the 

 stimulation of alcohol. This stimulation, however, is of short duration 

 and is invariably followed by a period of depression and inertia. In this 

 latter state, a man will do less work than before. In larger quantities, 

 alcohol has the effect of completely paralyzing the nerve centers. This 

 is seen in the case of a man " dead drunk." He falls in a stupor because 

 all of the centers governing speech, sight, locomotion, etc., have been 

 temporarily paralyzed. If a man takes a very large amount of alcohol, 

 even the nerve centers governing respiration and circulation may become 

 poisoned, and the victim will die. 



In an article in the Journal of Inebriety, Dr. J. W. Grosvener of Buffalo 

 says : " Alcohol is a paralyzer. The truth of this proposition has been 

 demonstrated experimentally scores of times by world-famed physiolo- 

 gists. Says Forel : ' Through all parts of nervous activity from the in- 

 nervation of the muscles and the simplest sensation of the highest activity 

 of the soul the paralyzing effect of alcohol can be demonstrated.' Several 

 experimenters of undoubted ability have noted the paralyzing effect of 

 alcohol even in small doses. By the use of delicate instruments of precision, 

 Ridge tested the effect of alcohol on the senses of smell, vision, and mus- 

 cular sense of weight. He found that two drams of absolute alcohol 

 produced a positive decrease in the sensitiveness of the nerves of feeling, 

 that so small a quantity as one-half dram of absolute alcohol diminished 

 the power of vision and the muscular sense of weight. Kraepelin and 

 Kurz by experiment determined that the acuteness of the special senses 

 of sight, hearing, touch, taste, and smell was diminished by an ounce of 

 alcohol, the power of vision being lost to one third of its extent and a 

 similar effect being produced on the other special senses. Other investi- 

 gators, as Crothers, Madden, Kellogg, Frey, Von Bunge, have reached 

 like conclusions." 



