1082 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



strong commercial or 97 per cent, alcohol, and afterwards saturated 

 with oil of cloves, the embryos are placed in a watchglass containing 

 a melted mixture of chloroform and paraffin in equal parts, in which 

 they may remain twenty or thirty minutes at a temperature not abovo 

 150° Fuhr. When saturation is complete, tho eggs have the same 

 appcaranco in the melted mixture as in alcohol. 



b. Prom tho above they arc transferred to another larger dish, 

 containing pure paraffin, which melts at 158° Fahr., but which must 

 on no account be allowed to boil. Here they remain for twenty to 

 thirty minutes moro. 



c. The embryos are then transferred, one or two at a time, to a 

 common slide, such as is used for mounting objects. The slide may 

 be warmed ovor an alcohol lamp. A brass ring, 5 to 8 mm. deep, 

 and 24 mm. in diameter, is then placed on the slide around the object. 

 This ring is then filled with melted paraffin, and the object arranged 

 in it in the desired position, with a hot needle, when the whole is left 

 to cool. 



d. After cooling, the paraffin contracts within the ring, when the 

 latter may be removed, and the discoidal block may then easily be 

 loosened from the slide. The block may then be trimmed down with 

 a scalpel, into a shape suitable for fastening into the well in the 

 carriage of a sledge microtome, or the block may be marked and laid 

 away until it is wanted for use. 



Nachet's Microtome. — This microtome (fig. 238) is distinguished 



Fig. 238. 



from previous models by several innovations. The knife-carrier 

 slides on an agate plate and is provided with four points of agate to 



