892 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



under alcohol on a principle analogous to that which Prof. Malassez 

 introduced in his modification of the Hoy Microtome. That is, the 

 instrument when used for immersion cutting is merely turned over 

 on its side, so that it is at right angles to the position it occupied 

 when used for dry cutting. Figs. 187 and 188, representing the in- 

 strument in both the positions in which it is used, are sufficient to 

 explain the way in which the instrument works. 



The microtome is chiefly intended for large sections, and is 

 apparently able to produce thinner ones than can be obtained by the 

 Katsch machine, the prototype of immersion microtomes. 



Microtome Knives.* — Dr. A. Brass points out that the sine qua 

 non for producing good sections is the knife, for with an indifferent 

 machine and a good and well-sharpened knife, better results will bo 

 obtained than with an indifferent knife and a highly complicated 

 instrument such as the Tboma-Jung microtome. 



For ordinary purposes the author uses a short knife made of very 

 hard steel. It is quite straight, 14 cm. long (8 cm. blade, 6 cm. 

 handle). The blade is 20 mm. broad and the back 5 mm. thick. 

 The under surface, continued into the handle, is flat and the upper 

 surface hollow-ground. When used it is worked at an angle of 

 about 10° to the surface to be cut. The knife is sharpened by means 

 of a special apparatus, the section of which is represented in fig. 189. 

 The wooden block /*, made of ash, is prismatic in shape, with a 

 central slit for the reception of the blade m, and is so constructed 

 that the cutting edge shall move against the hone s, at the same anglo 



Fig. 189. 



Fig. 190. 



as when used for cutting. The blade is fixed in the sfit by two 

 screws a, 5 cm. apart. By this contrivance the edge is rendered 

 wedge-shaped, and it is this characteristic which, the author thinks, 

 gives it its value. 



From fig. 190, giving a view of the knife m in operation, may be 

 gathered the relation of the knife to the object o and the section s', 

 and also the exact shape of the knife. After sharpening on the hone, 

 the finishing touches are imparted to the edge on the regulator strop, 

 so condemned by Gottschau. 



Preparing Adhering Series of Sections.f — For saving time in 

 the preparation of series of sections Dr. A. Brass advises the method 



* Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 305-7 (2 figs.), 

 t Ibid., pp. 307-8 (1 fig.). 



