JANUAEY 24, 1896.] 



SCIENCE. 



115 



bals to allow for free motion in vertical and 

 horizontal planes. The front of the eye 

 carries an elastic lens, made by fastening 

 a sheet of gelatine over a water chamber 

 with a glass back. The gelatine is bulged 

 more or less, as the water pressure in the 

 chamber is increased or diminished by rais- 

 ing or lowering the reservoir connected 

 with it by rubber tubing. A portion of the 

 retina is represented, including the yellow 

 and blind spots and serves the purpose of 

 a screen for receiving the images of can- 

 dles used with the model for studying the 

 optics of vision. 



The optical conditions involved in normal 

 vision, accommodation to near and far ob- 

 jects, the use of the iris, near and far sight 

 and correction by lenses, the blind spot, 

 corresponding points of retinae (two mod- 

 els), binocular vision and convergence, 

 estimation of distance, Scheiner's experi- 

 ment, etc., may be experimentally studied 

 with the model. 



12. J. G. Curtis : A method of recording 



muscle curves. 



Dr. Curtis briefly referred to a method of 

 recording muscle curves so that they shall 

 be visible to a large lecture class, such as 

 commonly calls for the use of the duBois 

 ' muscle telegraph.' 



The shaft of a muscle lever of Tiger- 

 stedt's form is replaced by a stout and very 

 long straw which shall magnify the con- 

 tractions as much as possible. In a cleft 

 in the free end of this straw is stuck a 

 piece of leather, which is to ' write ' upon a 

 drum turned simply by hand. The leather 

 should be about 2\ centimetres long, and 8 

 to 10 millimetres wide, the length of the 

 leather lying in the length of the straw. 

 The leather should be flexible, but thick 

 enough to be moderately elastic ; its rough 

 side should be turned toward the driim, and 

 longitudinal cuts, each about 6 to 8 millime- 

 tres deep, should be made with scissors in 



its free end, so as to divide what is to an- 

 swer to a ' writing point ' into five or six 

 fingers. 



The straw lever should be placed normal 

 to the drum and pushed directly toward the 

 latter until the cloven end of the leather 

 not only touches the drum, but is deflected 

 rather sharply in the direction toward 

 which the latter is to revolve. 



If now the drum be made to revolve by 

 band, there may be recorded very sufficient 

 muscle curves, each made up of several 

 neighbormg parallel lines, which lines are 

 visible together at a distance as a white 

 band from 4 to 10 millimetres wide. 

 13. G. K. Stewart : Measurements of the 



eiradation time of the retina. 



Dr. Stewart demonstrated for the par- 

 ticular case of the retina a method of meas- 

 uring the circulation time employed by him 

 for various vascular tracts. A solution of 

 methylene blue in normal saline was in- 

 jected into the central end of one jugular 

 vein of a rabbit. The retina on the other 

 side was observed with the ophthalmoscope, 

 and the interval between the appearance of 

 the blue in the central artery and in the 

 central vein measured with the stop-watch. 

 The following is a specimen experiment: 



Eabljit, 1360 grms, in weight. 



Circulation time from central artery to central vein 

 of retina, 1.75, 1.8, 1.7, 1.95 seconds. Last seen to be 

 rather too long. 



Circulation time from jugular vein to retinal artery, 

 4.05 seconds. 



Circulation time from jugular vein to carotid artery, 

 2.8 seconds. 



Circulation time from jugular vein to retinal artery, 

 3.8 seconds. 



Circulation time from retinal artery to retinal vein, 

 1.8 seconds. 



Circulation time from retinal artery to retinal vein, 

 1.85 seconds. 



Circulation time from jugular vein to retinal artery, 

 4.0 seconds. 



Circulation time from jugular vein to carotid artery, 

 2.25 seconds. 



Circulation time from jugular vein to carotid artery, 

 2.5 seconds. 



