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ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 171 



carrier by a large screw. The short clamp c holds the razor (or even a 

 microtome-knife). The ball-and-socket joint allows extensive motion in a 

 horizontal direction, but the vertical movements, although sufficient, are 

 more limited. 



This simple accessory is intended chiefly for those microtomists who 

 sharpen their own razors, and the only defect (which is pointed out by the 

 inventor), is that it requires a certain amount of space between the slide 

 and the object-carrier. 



Determining the Reciprocal Positions of Object-points.* — For this 

 purpose Prof. H. Strasser uses very thin paper ruled with fine lines as in 

 fig. 28, and further subdivided by coarse vertical lines in such a way that 

 the distances between ah -\- ef = c d and 



be = de. A quadrilateral case is then Ftg. 28. 



formed of the paper thus ruled, by gum- a, 1> c. d- e £ 



ming the ends together so that the line/ "Sffi 

 coincides with the line a. Within this 

 case, supported by a metal box, the speci- 

 men is imbedded. Owing to the thinness 

 of the paper no difficulty is experienced 

 in making sections if the mass be cut 

 with a very sharp knife. Each section is thus surrounded by a paper 

 band in which vertical and horizontal marks are present. These marks 

 are intended, inter alia, to aid in the recognition C'f the position of the 

 section to the object. 



Section-series and a new method for making Wax Modelling-plates.f 

 — Prof. H. Strasser, in an article on the study of section-series, and on a 

 means for facilitating the reconstruction of the dissociated form, describes 

 an improvement and simplification of the plate-model system devised by 

 Born,+ consisting in the adoption of transparent plates which are also 

 much thinner than any hitherto used. 



The apparatus required in the preparation of the new plates are an 

 iron roller, 4 cm. in diameter and 30 cm. in length ; a water bath for 

 keeping the wax at a temperature of 60^; some strips of tin and brass 

 from 0*2 to 5*0 mm. thick, and a large smooth lithographic stone. 



In preparing the wax plates, a piece of the still warm wax is kneaded 

 out in the hands as flat as possible, and having been placed between two 

 leaves of parchment paper kept moistened with turpentine, is rolled out by 

 means of the roller previously warmed. The thickness of the lamella is 

 regulated by the choice of the metal strips placed along the sides of the 

 paper. When a perfectly flat layer has been thus rolled out, the parchment 

 paper is stripped off and the plate dried between filter papers. To the 

 surface of these wax plates paper is made to adhere by means of gum, for 

 which purpose flour is first rubbed into the plate, or by melting it in by 

 means of a hot roller. The plates thus produced are of fair size, and 

 from 1/3 to 1/4 mm. thick. 



In preparing wax-paper plates to which the section-sketch is attached, 

 a very similar procedure is carried out. This method is to be preferred to 

 the former as a rule. One of the leaves of tracing paper is placed on the 

 lithographic stone damped with turpentine. On the other side is laid a 

 strip of metal, then the wax is spread over the surface and the second leaf 

 of tracing paper having been adjusted, a flat lamina is produced by rolling 

 as before with the heated roller. The thickness of these plates, paper and 



* Zeitschr. f. Wiss. Mikr., iii. (1886) pp. ]92-5 (1 fig.). 



t Ibid., pp. 179-92 (1 fig.) . % See this Journal, 1884, p. r,84. 



