long, preferably of some thin material. The writer has found 

 tnat'ormnary green opaque window blmds can be sized black 

 so as to become practically light-proof, and as it is advisable m 

 constructing a light trap to have two blinds, he finds that with 

 two such blinds the hgnt is wholly excluded, and if necessary 

 the room can be used as a photographic dark room. The wood- 

 en rollers used are of the ordinary pattern and present no spe- 

 cial peculiarity. They are built in or boxed in at the top in a 

 light-tight manner. 



We turn next to the various sleeves sliding on the long U].- 

 right girders. Of these one of the most important is the right- 

 hand lower sleeve which carries a leg-of-mutton shaped table 

 for use in connection with the production of camera lucida 

 drawings. I'his sleeve as well as all the others, is balanced with a 

 sasii-weight, so that it moves with the utmost freedom either up 

 or down through a space of about four feet. The table may 

 therefore be placed within fifteen inches of the floor, or it rhay 

 be raised to a distance of three feet. This abjustability is found to 

 be highly convenient in the production of camera lucida draw- 

 ings of definite magnification. The peculiar shape of the table 

 has been evolved from practical experience during many years. 

 In g'eneral, its form is such that when taken together with its 

 mate on the other side of the microscope, it presents a semi- 

 circular curvature which gives the investigator a free play for 

 hands and body. This table is painted black, as are all the other 

 accessories used in this system. See 32, 34, Fig. i. 



Turning to the left-hand side of the microscope, we find an 

 entirely similar and symmetrical sleeve and table, which however 

 is used for a very difJerent purpose. This sleeve carries the 

 mate to the camera Jucida table and of course, in the case of a* 

 left-handed operator, could be used in the same way as the right- 

 hand table would be used by a right-handed operator. The 

 rftual position for the left-hand table is about on a level with 

 the microscope stage. This height is found to be convenient 

 for several reasons; first, under ordinary circumstances, it is 

 about ordinary table height and is convenient for supp'orting the 

 dissecting microscope, which, as explained later on, has a special 

 illumination of its own. Thus in the preparation and ex:.mina- 

 tion of objects, the dissecting stand is as close as possible 

 to the examination stand and the objects may be transferred 

 from one to the other with the greatest convenience; a second 

 reason for having the left-hand table on a level with the stage 

 of the microscope is that the preparations may be moved on and 

 ott the stage of the microscope with the least danger and with 

 the greatest facility. A third reason is that in this position the 



