708 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



important part of the process, and should not be hurried. Now place 

 the piece in a shallow dish and add pure balsam enough to cover 

 it and evaporate to hardness, being careful not to raise the heat above 

 1 10 F. When the balsam is hard the section may be worked down 

 to suit. The balsam will hold the soft parts in position while this 

 is being done. Uso water as a lubricant for this part of the work. 

 The section made to suit, dissolve out the balsam with benzoic, place 

 in absolute alcohol for a day, clear again in clove oil and mount. 



Sections made in this way are necessarily somewhat thick for 

 the reason that the different parts which it is desired to show in the 

 section seldom lie in the same plane, consequently they are best 

 mounted in a cell ground into the slide, which allows the cover-glass 

 to be brought down close. The method may seem somewhat tedious 

 and certainly requires some patience, but the results more than 

 repay for the trouble. Dammar will be found the best medium for 

 mounting. 



Henking's Microtome Object-holder for accurately adjusting 

 the Object. :j: — Dr. H. Henking's object-holder (fig. 147) aims at 

 giving a measureable rotation to the holder by means of adjusting 

 screws, so that sections may be cut at definite angles to one another. 

 The clamp a, made in a curved form for convenience in holding 

 curved objects and to avoid interference with the knife, is connected 

 with a ball-and-socket joint contained in e s, which can be fixed when 

 necessary by the screw r. The movable half of the clamp slides 

 upon the guides k k and is adjusted by the screw b ; in the fixed half 

 are two cylindrical holes directed accurately towards the centre of 

 the ball joint, i and %' are two rods which slide in these holes, and 

 their extremities are hinged at m and m' to two long screws which are 



raised or lowered by the nuts d 

 and d' fixed in position, but free 

 to turn in the collars c and c'. 

 By means of these nuts, therefore, 

 a rotation can be given to the 

 clamp about either of the axes i or 

 i', and may be measured by divi- 

 sions upon d and d'. The screw 

 which works in d is only half as 

 long as that at d', because the 

 object can be roughly adjusted in 

 this direction in the jaws of the 

 clamp, and d is only required for 

 small motions. On the plate 

 which covers the ball-and-socket 

 joint is a vernier scale for indicating the thickness of the sections. 

 By pushing the object-slide along for distances between 1 mm. and 

 1/40 mm., sections can be obtained without any further assistance 

 than that of a sharp knife. 



* Zeitschr. f. Wiss. Mikr., i. (1884) pp. 491-6. Cf. Zeitschr. f. Instru- 

 roentenk., v. (1885) pp. 314-5 (I fig.). 



