ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 



165 



Fig. 41. 



They have all the advantages of the former, and are of all sizes and 

 very cheap. 



Imbedding-Box.* — A convenient box (fig. 41) introduced by Dr. 

 Dimmock,f may be made of two 

 pieces of type metal (or better of 

 brass), each piece of metal having 

 the form of a carpenter's square. 

 A convenient size will be found 

 in pieces measuring 5 cm. (long 

 arm) by 3 cm. (short arm) and 

 7 mm. high. With such pieces a 

 box may be constructed at any 

 moment by simply placing them 

 together on a plate of glass which 

 has previously been wet with glycerin, and gently warmed. The 

 area of the box will evidently vary according to the position given to 

 the pieces, but the height can be varied only by using different sets 

 of pieces. 



Orientation of Small Objects.| — Orientation becomes difficult 

 only with objects so small that their position can be controlled only 

 by the aid of a Microscope. Spherical objects, less than 1 mm. in 

 diameter, e. g., many ova and embryos, are the most difficult to 

 manage. Such objects may usually be successfully oriented in the 

 following manner, as given by Dr. C. 0. Whitman: — • 



1. Prepare the box ; for this it will be necessary to use the two 

 triangular pieces of metal, a rectangular glass plate (2 in. by 2^ in.). 

 The plate should be cleaned and then smeared with glycerin, and 

 the pieces of metal so adjusted that the arms are parallel with the 

 edges of the plate. 



2. Having warmed the box over a spirit-lamp, lift the object from 

 the basin of paraffin by the aid of a small, flat, thin spatula (first 

 starting it from the bottom by shaking the paraffin a little), and allow 

 it to flow with the paraffin carried on the spatula into the box. 



3. Then fill the box, 5-6 mm. deep, with the melted paraffin, and 

 warm it a little over a spirit-lamp, just enough to keep all of the 

 paraffin in a liquid condition for a few moments. Now place the box 

 on a warm table of a dissecting Microscope, and by the aid of a hot 

 needle proceed to place the object in the desired position. As the 

 object is illuminated from below, it can be easily seen, turned over, 

 and moved about at pleasure. If the paraffin sets before orienta- 

 tion is effected, it should be melted again as before, and the needle 

 must be kept hot by repeatedly holding it in the flame of the lamp. 



The difficulty of finding very small objects in a basin of paraffin 

 will be very much lessened by keeping the paraffin free from dust, 

 and the bottom of the basin (tin) scoured bright. A piece of emery 

 cloth serves for polishing. 



The necessity of re-warming the box of paraffin, which often arises 



* Amer. Natural., xix. (1885) pp. 12i7-8. 

 t Of. this Journal, ii. (1882) p, 881. 

 X Amer. Natural, xix. (1885) p. 1248. 



