764 



(letennined by a physiological properly, \iz. the power of' con- 

 traction of its Hccoiniiiodatioii-muscle ; tlie physiologic near |)oini. 



He8s says that it is almost generally assumed that every increase 

 in lens-fraclion of one dioplrie exacts an equal increase of the 

 contraction of tlie ciliary innscle. 



Although this simple relation is not self-evident, considering the 

 complicatedness of the accommodation-process, we will acce|)t it for 

 a moment, in order to try and pi'ove it, taking as unit of contraction 

 of the ciliary muscle, the contraction necessary to bring the accom- 

 modation from to I dioptrie, which unit we can call ,,myodioptrie". 



If Hess' unproved supposition is correct, one will need a conti-action 

 of 10 myodioptries in order to bo able to accommodate 10 dioptrics. 

 We can now also ex|)ress the total powei- of the accommodation- 

 muscle in myodioplries, for in an emmetropic person this will be 

 the reciprocal value of the distance of the physiological near point, 

 or otherwise ex|)ressed, il will be equal to the number of dioplries 

 one could accommodate if the lens had an unlimited elasticity. 



So we stand here before the following two questions: 



h. Is the myodioptrie for one person a fixed unit? That is to say : 

 is il contraction of the accommodation-muscle of one myodioptrie 

 necessary for every accommodation-increase of one dioptrie? 



c. How great is the power of the accommodation muscle expressed 

 in myodioptries? 



Other questions which rise before us are the following: 



(/. is it possible to detect the very slightest paresis of the 

 accommodation muscle? 



e. Is it possible to make curves of the paralysing influence certain 

 substances exert on the accommodation muscle? 



U|» to novv we were accustomed to determine the action of the 

 accommodation-muscle by finding the nearest point. 



Let us now suppose a person (fig. 1) who can accommodate 10 

 dioptries, and who possesses a power of the ciliary muscle amounting 

 to 24 myodioptries, then the accominodationmuscle can be more 

 than half paralysed, while the nearest point need not have changed 

 its place. In this way we only notice the possible presence of a 

 paralysis of the accommodation muscle, when it is far advanced. 



In consequence we know little about the paralysing action of 

 certain substances which only slightly affect the accommodation 

 muscle, even about those substances which we use daily, such as 

 cocaine. We find the most divergent communications in the literature 

 about the paralytic action of cocaine on accommodation. 



Some writers assert that it does not act at all on the accommo- 



