820 



SUMMARY OF OUBRENT EE8EARCHES RELATING TO 



Fig. 138. 



after the chloroform has evaporated. The vessel is then exposed to 

 a temperature which corresponds to the melting point of the paraffin 

 employed. The paraffin melts and the chloroform evaporates, so 

 that the object is brought very gradually into pure melted paraffin. 

 In this way the object becomes completely saturated with the paraffin. 

 It is essential that the mixture be kept at the proper temperature 

 until all the chloroform has evaporated. A simple test is to place a 

 hot wire in the paraffin, if no bubbles arise it 

 is safe to conclude that the chloroform has 

 entirely escaped. 



After evaporation of the chloroform the 

 object may be placed in any desired position, 

 and the paraffin allowed to cool. After cool- 

 ing the object can be cut out and fixed to a 

 larger block of paraffin fitted for the holder 

 of the microtome. 



Boxes for imbedding may be made of 

 rectangular pieces of paper, of the thickness 

 of postal cards, in the following manner. 

 The paper is first broken in the lines a a' 

 and h h' (fig. 138), then c c' and d d' (by 

 bending always towards the same side). 

 Then in every corner a break (A A' BB' 

 C C D D') is made by bringing A c and A a 

 together. The four sides of the box are next 

 bent up, and the corners at the same time 

 turned outwards and back behind the ends 

 A B, a 6, and CD a' h'. Finally the upper edge of these ends is bent 

 down over the corners. 



Bubbles around the object may be removed by means of a heated 

 wire. 



Hoffmann's Imbedding Apparatus.* — Dr. F. W. Hoffmann de- 

 scribes the apparatus he has devised for the more accurate imbedding 

 of anatomical preparations, in which an air-pump is replaced by a 

 suction-pump in connection with a water supply of sufficient pressure. 



The suction pump S, which ought to have as free a discbarge as 

 possible, is connected with the exsiccator B by means of a strong 

 non-compressible indiarubber tube (or one with a glass tube inside 

 it). The exsiccator contains a few small bowls P, filled with paraffin. 

 The whole is placed in a zinc vessel W, filled with water, and so ar- 

 ranged that the temperature remains constant. Between S and E is 

 the flask F (with strong sides), which is connected with the india- 

 rubber tube by a T piece. A glass tube m passes into a bottle of 

 mercury Hg, and serves as a manometer. The object of the flask is 

 to prevent the entrance of the water into E in case of any difference 

 of pressure in the pipes. The manometer enables the pressure to be 

 read directly, and enables one to judge whether the preparations are 

 sufficiently penetrated with paraffin. 



* Zool. Anzeig., vii. (1884) pp. 230-2 (1 fig.). 



