510 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 149. 



paraffin wax mixture, in which were three parts of white wax to one of soft 

 paraffin. The objects were gradually cooled, and sections were made at a 

 temperature of at least 17^ E. Schanze's microtome, which is regulated 

 to cut sections from 1/100 to 1/150 mm., was used, and the objects were 

 fixed by Giesbrecht's method. In cutting sections it is important to begin 

 at the hinder end or to follow the direction of the hairs. 



Orienting Objects in ParaflBn.* — Mr. E. A. Andrews has improved the 

 method of Dr. Selenka f for keeping paraffin melted while the contained 

 small objects are being arranged under the Microscope 

 in any desired position, and then rapidly cooling the 

 paraffin without disturbing the position of the objects. 



Finding it difficult to make tubes such as Prof. 

 Selenka described, which should be of such shape as to 

 admit of removing the hardened paraffin readily, and at 

 the same time with depressions of sufficient size for any 

 but very minute objects, Mr. Andrews made use of the 

 following simple device, which, though more clumsy 

 than the tube of Selenka, can be used for objects 1 mm. 

 long and much larger, while giving a block of paraffin 

 of very regular shape and with rectangular sides. 



A common flat medicine bottle is fitted with a cork 

 through which two tubes pass, or, if the mouth is small, 

 one tube may be fastened into a hole drilled into the 

 bottle. One of these tubes A is connected with hot and 

 cold water; the other B is a discharge-pipe for the 

 water entering the bottle by A, and raising or lowering 

 its temperature as warm or cold water is allowed to flow 

 in. On the smooth flat side of the bottle four pieces of 

 glass rods or strips are cemented fast, so as to inclose a 

 rectangular space C, which forms a receptacle for the 

 melted paraffin. As long as the warm water circulates 

 through the bottle the paraffin remains fluid, and objects 

 in it may be arranged under the Microscope by light 

 from above or below, and can be oriented with reference 

 to the sides of the paraffin-receptacle or with reference 

 to lines drawn upon the surface of the bottle. When the cold water is 

 allowed to enter in place of the warm, the paraffin congeals rapidly, and 

 may be easily removed as one piece. The discharge-pipe should open 

 near the upper surface of the bottle, to draw oif any air which may 

 accumulate there. 



Orienting Small Objects. | — It is frequently a very difficult matter to 

 properly orient small objects, especially spherical eggs, so that sections 

 may pass through any desired plane. In working on the embryology of 

 the common shrimp, Mr. J. S. Kingsley found the following process very 

 convenient : — Impregnation with paraffin is accomplished in the usual way, 

 and then the eggs (in numbers) in melted paraffin are placed in a shallow 

 watch-crystal. 'J'hey immediately sink to the bottom, and then the whole 

 is allowed to cool. The crystal, glass upwards, is now placed on the stage, 

 and the eggs examined under a lens. In this way one can readily see 

 exactly how any egg lies, and then with a knife it may be cut out with the 

 surrounding paraffin, and in such a way that it can readily be fastened to 

 the block in any desired position. After all which have been dropped in a 



* Amer. Naturalist, xxi. (1887) pp. 101-2. 

 + IW\(]., p. 102. 



t See this Jourual, 1885, p. 1086. 



