710 SUMMARY OF CURRENT RESEARCHES RELATING TO 



chitinous skeletons of insects, there is an attachment with a very stout 

 blade, on the principle of a carpenter's plane d, whicli screws on to the 

 carriage in place of the knife, and like the knife it can be used straight 

 across or obliquely. 



Diameter of well j, 7/8 in. ; depth of well, 1^ in. ; depth of well with 

 chuck L, 1 in. 



For cutting soft material, paraffin may be cast directly into the well, 

 or into a chuck (not shown) which is held firmly by being screwed into 

 the bottom of the well. The adjustable chuck L is intended for harder 

 material. 



Microtome No. 1 gauges to 1/10,000 of an inch by turning the 

 rachet g one click, but can be set to any desirable thickness less by the 

 adjustable arc N. No. 2 gauges to 1/2000 inch, adjustable like No. 1. 



Paoletti's Improved Microtome.* — In Sig. V. Paoletti's improved 

 microtome the advantage aimed at consists in reducing the number of 

 movements, and thus to diminish the tendency to inequality in the thick- 

 ness of the sections. With this intent the knife is kept fixed, and the 

 object-carrier alone moves. The microtome stand consists of a heavy 

 cast-iron base, to which is fixed a vertical upright. To this latter is 

 pivoted a largish steel plate at the end of two horizontal arms. To this 

 plate is fixed the object-carrier, which receives horizontal and vertical 

 movements from a micrometer screw placed beneath it, and with which 

 it is connected by means of a special arrangement. 



The knife is fixed by a clamp in any desired position to the vertical 

 upright. 



On a dial-plate, the index of which points against the steel plate, are 

 marked numbers from 1-12 ; these correspond to hundredths of a milli- 

 metre, and serve to indicate how far the object-carrier ascends while it is 

 moving horizontally at the same time. 



Method for keeping Serial Sections in order during manipula- 

 tion.! — l)r. L. Darkschewitsch has used the following method for four 

 years for keeping sections of brain and cord in their proper order. A 

 glass tube or wine-glass of the diameter of the sections to be cut is filled 

 with spirit. Discs of filter-paper are also cut of the size to conveniently 

 fit within the vessel. These paper slips are numbered, and having been 

 arranged in their proper order, soaked in spirit. As the sections are 

 made, the paper slip is laid thereon, the two drawn off together, and laid 

 in the vessel, the paper side downwards. 



When the vessel is full of the serially arranged sections, the whole 

 series may be stained in situ. For this purpose the spirit is poured off, 

 and, if necessary, the series is washed with distilled water before the 

 staining solution is poured in. If Weigert's liaBmatoxylin method is to be 

 used, the solution is poured in after the spirit has been removed, and the 

 glass vessel is then placed in a hot box for twenty-four hours. The 

 staining solution is then poured off, and the series washed with distilled 

 water until no more dye is given off. The sections are next taken out 

 separately, and placed on a flat vessel (e. g. a plate) filled with the 

 decolorizer, wherein they remain until the decoloration is complete. 

 After having been thoroughly washed they are returned to the glass 



* Atti della Societk Toscana di Scienze Natural!, vi. (1888) p. ISO, 

 t Zeitschr. f. Wiss. Mikr., vi. (1889) pp. 43-5. 



