II. OPHTHALMOLOGICAL. 935 



adjusted a second axle, round which turns a rod containing four coloured 

 wafers, or beads, or ignited pieces of German tinder, forming the same figures 

 as are shown by the bead of Wheatstone's photometer. These figures can 

 be changed by differently fitting the india-rubber band behind the black board. 

 Made and invented by J. van Dreeven, Amanuensis of the Physical Cabinet 

 of Utrecht University. 



3685. Coccius' Polarising Ophthalmoscope. 



E. Stohrer, Leipzig. 



Design of Apparatus. To investigate the eye with perfectly polarised 

 light, the images being either erect or inverted. 



Practical Application. To determine the defects of transparency on the 

 iris, the cornea, and refracting media of the eye, with reference to the degree 

 of nebulosity in the retina, to facilitate the estimation of the degree of atrophy 

 of the optic nerve, and by removing all reflections to obtain a more distinct 

 view of the fundus. 



3710. Couper's Ophthalmoscope, with five discs and 45 

 lenses, two mirrors which are adjustable for right or left eye. 



T> Hawksley. 



3679. Micrometer, for measuring objects in the fundus oculi. 



Prof. Laqucur, Strasburg. 



This apparatus is used for measuring in the living eye the real size of the 

 " papilla," the diameter of the blood vessels of the retina, the size of the 

 macula lutea, the distance of the latter from the external edge of the blind 

 spot, also the dimensions of any extravasations of the retina. 



For the method of using the apparatus, see Centralblatt der med. Wiss. 

 1873, No. 59. 



It can also be used for determining -the condition of the refrangibility of 

 the eye in ophthalmoscopic examination, by placing the toothed part of the 

 stems in front of the lamp which serves as a source of light. 



An account of the apparatus is published in the Proceedings of the Oph- 

 thalmological Society of Heidelberg for 1875. 



3687. Coccius' Micrometer for the Eye. 



E. Stohrer, Leipzig. 



Design of Apparatus. To measure the transparent and sensitive parts 

 without contact. 



Practical Application. To observe any object in the cornea, scars, opacities, 

 cloudiness of the pupil in diseases, the degree of movement of the iris, or 

 the widening of the pupils by the inspiration. 



3669. Instruments for Extraction of Cataract. 



Dr. Adolph Weber, Darmstadt. 



3678. Hose's Schistoscope, for the physiology of colour. 



F. Schmidt and Haensch, Berlin. 



3691. Apparatus for demonstrating the Reverse Position 



of the Image on the retina of the observer's own eye. (Old.) 



Prof. Dr. Dove, Berlin. 



3705. Dr. Archer Warwick's Endoscope. T. Hawksley. 



