Chapter XVI: Some Embryological Methods 125 



as above, before they are placed in the paraffin bath, by a mixture of 

 clove oil and collodion of about the consistency of thick molasses, as in 

 Patton's method (Zeitschrift filr wissenschaftliche Mikroskopie, Vol. XI 

 [1894], p. 13). One or a number of small objects which have previously 

 been cleared in oil of bergamot or cloves are mounted in small separate 

 droplets of the reagent and oriented under a dissecting lens with refer- 

 ence to the ruled lines. The paper is then placed in turpentine which 

 washes out the clove oil and fixes the object in place. The paper with 

 objects attached is then passed through melted paraffin and imbedded in 

 the ordinary way. Upon removal of the paper from the hardened block 

 a sufficient number of pencil marks remain to be used as a guide in sec- 

 tioning. Instead of pencil marks Patton employed ribbed paper. 



II. For celloidin sections 



Eycleshymer's Methods. a. For imbedding, metal boxes made of two 

 Ls (Fig. 30) are used. The Ls are held together by overlapping strips. 

 The ends and sides of the box are perforated at regular intervals by 

 small holes which have been drilled opposite one another in such a way 

 that threads drawn through them are parallel. Threads of silk are run 

 through the holes from side to side, drawn taut, and cemented to the 

 outside of the box with a drop of celloidin. Each piece of thread should 

 have an end two or three inches long hanging outside the box. A piece 

 of heavy blotting paper is used as a bottom for the box. The object is 

 oriented on the parallel threads and the imbedding mass poured in and 

 hardened. The loose ends of the threads are then soaked in a solution 

 of thin celloidin which contains lamp-black, the celloidin drops holding 

 the threads taut are dissolved by a drop of ether-alcohol, and the black- 

 ened ends are drawn through the block of celloidin. The lamp-black 

 leaves distinct black lines through the mass which will serve for properly 

 orienting the celloidin block on the microtome. 



This method is valuable also in reconstructions from sections (see 

 chap. xvii). In such work it is very desirable to establish "reconstruc- 

 tion points " to guide in fitting the wax plates together properly. The 

 black rings of lamp-black left in the sections answer admirably for this 

 purpose. 



b. For small objects in which reconstruction points are not required 

 Eycleshymer uses fine insect pins from which the heads have been 

 clipped and the headless ends loosely inserted in handles. The objects 

 are mounted on the points of the pins and oriented in the desired posi- 

 tion. Each pin is then removed from its handle, and the free end is 

 inserted from below into a small perforation which has been made by 

 passing a somewhat larger pin lengthwise through a cork. A number 

 of pins may be mounted on the same cork. To prevent the objects from 

 becoming dry the cork must frequently be inserted into the mouth of a 



