1916 Journal of the American Medical Association  
finger lifts it at sufficiently short intervals we get a curve very similar to the curve given by Dr. Howe, but when a lighter weight is employed and the finger contracts less frequently, we get another type of curve. Under these con¬ ditions it may contract indefinitely, there is no falling off from fatigue because the muscle is working within its capac¬ ity. Dr. Williams and I tested the accommodation virtually in the manner described by Dr. Howe, except that our apparatus was not
more » ... ng. Thus, moving the object toward the eye and receding, and eliminating certain sources of error, we found, even after keeping it up far longer than Dr. Howe, say IS to 30 minutes, that there was no falling off, that is, the ciliary muscle was working within its capacity and showed no fatigue, just like the finger with the light weight. We then tried a much more severe test of the accom¬ modation, holding the test object as near the eye as possible without blur and keeping it there continuously at the near point and if possible moving nearer, and we got a third curve. Instead of the muscle weakening and the accommoda¬ tion falling off, the accommodation increased for IS to 30 minutes. Thus we found that it is not easy to fatigue the ciliary muscle, and that is" practically the testimony of experience. We know that we can read for hours, exercis¬ ing considerable accommodation. It is because the work of the ciliary muscle is so excessively small when measured or estimated in foot pounds; it only has to relax the zonule. It can do this without showing any fall¬ ing off from fatigue, but on the contrary an increase. Possibly in myasthenia gra¬ vis or other very exceptional condition, one might get curves like those of Dr. Howe but if certain sources of error are eliminated the curve of accommodation will show no fatigue under Dr. Howe's test. Dr. E. E. Blaatjw, Buffalo : At a more advanced age we cannot study through the nearpoint determination the contractility of the ciliary muscle, but only the plasticity of the lens. This prevent us from diagnosticating paral¬ ysis of the accommodation, especially of the ciliary muscle in patients older than 60 years. As to the remarks of Dr. Savage about neuricity, etc., I would like to call attention to the investigations of Prof. J. Boeke of Leiden, who has shown that all muscles have a double innervation, one from the cerebrospinal organs and one from the sympathetic system. Dr. George H. Price, Nashville, Tenn. : In the case of the curve represented by Dr. Lancaster there is a7 constant and accelerated impulse to the muscle. There is the increased discharge of neuricity as the act is performed. Therefore, if there is continuous stimulation of the same character throughout the impulse, then, since it maintains a perfectly smooth curve, the muscle is the organ at fault when it begins to recede ; the muscle grows weaker. But if the curve is not perfectly smooth from its beginning to its end, it shows a variation in the neuricity or impulse. Therefore that would indicate nervous fatigue or failure. In the case of the sustained line, if that line showed a tremulous movement, up and down, then we would have a variable amount of neuricity or nervous impulse being sent to the muscle. Dr. Lucien Howe, Buffalo : As to the point brought up by Dr. Woods, it is true that the result of the first test would not be exact. We do not depend on doing the test once, but many times. The question asked by Dr. Savage is not one to be answered offhand. I know nothing about neuricity or whether it is the eighth or the tenth center, and the patient does not care. The question is, Is there fatigue? Dr. Lan¬ caster can work with a half pound dumbbell and get that kind of a curve. Physiologists have found the degree of strength that can lift a dumbbell a certain number of times. But it does produce fatigue, simply because the patient cannot lift it again and he knows it. I do not think there is anything very subtle or strange about that. It simply shows how far he can go and after awhile he cannot approach it at all, and we say it is run down. This work was done under the supervision of Prof. Frederic S. Lee of Columbia University, and he is an authority on the question of fatigue. I have simply dealt with accommodation in emmetropia ; but now I am studying ammêtropia and heterophoria, and the possibilities are enormous. After five years of work it seemed worth while to present the results.
doi:10.1001/jama.1916.02590020020006 fatcat:qn5xs76gkbf55gz6mjay25hlfm