and Laboratory Methods. 1679 



wards so that the lens may be lowered over the edge of the dissecting pan. A 

 lens thus supported may be swung around over a large specimen, and is conven- 

 iently focused by sliding the spiral up and down the brass rod. 



This apparatus, by the addition of another lens support, serves an excellent 

 purpose in the examination of small parts and dissections, and makes the use of 

 the microscope much easier for the beginner. In making use of the apparatus 

 for this purpose, it is arranged as follows : Upon the ring of the lower support 

 is placed a piece of non-drying modeling clay (to be purchased of dealers in art 

 and laboratory supplies). If the parts are to be examined dry, they are pressed 

 down into the clay and arranged as desired ; if they are to be immersed in water, 

 a depression of suitable dimensions is made, and in the bottom the parts are 

 secured. Water is now poured into the improvised pan and the specimen is ready 

 for observation. Should specimens transfixed by pins be used, they are easily 

 fixed and oriented in the clay. The holder is elevated to a convenient height 

 above the table, the lens is focused, and the observer may then examine the 

 specimen with one eye and, without moving the head, make the drawing. 



The modeling clay previously mentioned is useful in many ways. When irregu- 

 lar objects are to be held in position, either upon the table, easel, or wire support, 

 they may quickly and easily be secured by a piece of the clay. Small fragile 

 structures, such as the mouth parts of insects, are readily mounted in any position 

 by pressing them into the surface of the clay. Numerous other uses suggest 

 themselves in practical work which need not be mentioned. 



Aside from the two pieces of apparatus described, nothing more is required 

 for class use except dissecting pans and instruments. The former should be of 

 different sizes and may be made by pouring melted paraffin into suitable tin pans. 

 It is usually desirable to have projections of some sort in the bottom to anchor 

 the paraffin. For many purposes a black background is desirable, and this is 

 obtained by mixing lampblack with the melted paraffin. Small pans may be 

 made by using the bodies of the ointment boxes, the tops of which were utilized 

 as the bases of the lens standards. Small pasteboard boxes thoroughly soaked 

 in melted paraffin are light and convenient and last well. 



Improvised dissecting instruments, except needles, are not to be recommended. 

 Excellent ones, perfectly adapted to their purposes, may be purchased at reason- 

 able prices, and are always to be preferred. 



Some applications of the easel and lens supports are illustrated in the accom- 

 panying reproduction of a photograph. C. E. McClung. 

 University of Kansas. 



A Convenient Press for Obtaining Small Amounts of 



Plant Juice. 



It is often necessary in the physiological laboratory to obtain a small amount 

 of juice or sap from either leaves, stems, or roots of plants or to prepare an extract 

 of material from some part of a plant, either for chemical analysis or physical 

 measurements. 



