LABORATORY GUIDE L\ PHYSIOLOGY. 



Determination of the near point or "punctum prox- 

 imum." Determine the distance from the eye of the 

 nearest point at which a pencil point or needle may 

 be perfectly clearly seen. The exact location of the 

 near point may be more satisfactorily determined if 

 one look at the object through two holes, 2 mm. apart, 

 in a card. At this point thepunctum proximum act 

 of accommodation is brought most actively into play. 

 Determination of the punctum remotum. 



Direct the eye toward some object not less than 

 six meters away and describe to other members of 

 the division the minute details of the object, such as 

 slight irregularities of surface lines or other details. 

 If an individual is able to convince his comrades that 

 he can perceive, at this distance the minute details 

 of objects he must be credited with normal vision. 

 Inasmuch as he can also see with the usual distinc- 

 tions more distant objects the punctum remotum is 

 said to be located at infinity; or, to state it in another 

 way, the eye is able, with suspended accommodation, 

 to bring parallel rays to a focus upon the retina.* 

 (b) It frequently happens that the individual under 

 observation fails to make out more than the merest 

 outline of an object 6 meters away. Decrease the 

 distance until he is able to perceive details seen by 

 the majority of his comrades. If this distance has 

 to be decreased to two or three meters the determi- 

 nation may be made more exact by resorting again 

 to the needle and punctured card mentioned in (a), 

 and carrying the needle away until it appears double. 



*It must be stated here that this experiment does not make it cer- 

 tain that the punctum remotum is not beyond infinity! In a subsequent 

 lesson that point will-foe carried farther. We must be temporarily con- 

 tent with having it so far. 



