184 DE. G. LINTOSAY JOHNSON ON THE [Jan. 19, 



quite reconciled aud contented. I found that extreme gentleness, 

 together with petting the animals, o^^ercame their fears, so that 

 no force was needed ; nor, indeed, would 1 have suffered it to be 

 employed under any cii'cumstances. A few of the Monkeys and 

 Lemurs were observed in the Belle Yue Gardens, MauL-hester, 

 some in Mr. Jamrach's and Mr. Hamlin's collectious, and in various 

 travelling menageries, since they were not to be found in the 

 Society's Gardens. In all examples of 38 distinct species of 

 Monkeys and Lemurs were examined, including forms of every 

 genus which could be found In the Society's and other menageries. 

 All the observations were made by w hat is termed the direct 

 method with the ophthalmoscope, the instrument being used 

 within an inch of the animal's eye without an interposed mag- 

 nifying lens, thus presenting to the observer an upright picture of 

 lOdiameters' magnification. This method is preferable to the 

 indirect in which a lens is used, as the image then obtained is 

 inverted, and only of 3 to 4 diameters' magnification, which is 

 also less distinct than the larger upright image. In most cases 

 cocaine aud homatropine were dropped into the eye to obtain a 

 larger pupil and consequent!}' more light. 



The fundus of the fair European human eye appears, when viewed 

 with the ophthalmoscope, of an orange-red colour, pretty uniformly 

 distributed over the entire fundus ; only when we get towards the 

 confines of the visible field does the background become more 

 intermixed with streaks of pigment. A little to the inner or 

 nasal side of the centre of the field we observe the disc of the 

 optic nerve, of a pinkish colour and slightly oval shape, with the 

 major axis vertical. From the centre of this disc the scarlet arteries 

 and lake-red veins of the retina proceed, passing in every direction, 

 dividing into numerous branches. In the dark-coloured races the 

 appearances are similar, save that the orange-red bacliground is 

 replaced by a reddish brown, owing to the great increase of dark 

 pigment (see Plate II.). 



Only one part of the fundus is wholly free from vessels, and 

 that is at and around the maeida lutea or yellow spot. The 

 macula is a small pit or depression situated in the axis of vision, 

 about 2| disc breadths from the disc to the outer or temporal side. 

 It appears different in colour in the eyes of different individuals. 

 Generally it appears as a dark-reddish circular patch, with a bright 

 spot in the centre, and in some cases surrounded by a circular 

 glistening halo or ring, well defined on its internal margin, but 

 fading a^^av into the general background towards its external 

 border (marked d, Plate II.). Occasionally a second or even a 

 thii-d ring may be seen inside this large one, all having the fovea 

 as a common centre. 



The macula being in ourselves the seat of most acute vision, 

 considerable attention has been given to this highly differentiated 

 area, which has an actual diameter of about 1-5 mm. It is only 

 in this region, the size of a phi's head, that we see perfectly, our 

 acuteness of vision decreasing rapidly outside this region. In 



