ZOOLOaY AND BOTANY, MICROSCOPY^ ETC. 



511 



suitable position are thus cut out, the parafEn is again melted, and after 

 stirring the eggs the cutting out is continued as before. 



Method for Reconstructing Small Microscopic Objects.*— Dr. N. Kast- 

 schenko's method depends on the principle of obtaining two intersecting 

 and perfectly smooth surfaces which he terms definition planes. In respect 

 to the reconstruction of the object, he follows previous methods, especially 

 that of His. He imbeds his object in parafBn and stains the surface of the 

 block with lampblack dissolved in about ten times its bulk of turpentine. 

 The stained block a is in its turn imbedded in paraffin (fig. 150). The 

 accuracy of the surfaces is obtained by means of the machine (fig. 151) 



Fia 150. 



Fig. 151. 



invented by the author, and 

 intended to be adjusted to 

 the Schanze microtome. It 

 consists of a bar a bent 

 twice at a right angle : 

 through the ring 6 at its 

 upper end runs a bar, 

 terminated by a circular 

 disc <?, to which the pre- 

 paration e is attached : the 

 horizontal bar is fixed in 

 the desired position by the 

 screw c. 



The construction of the 

 object is effected in the 

 usual manner, and is divi- 

 sible into two chief groups, 

 surface construction and 



serial construction. For the former, transparent material, such as glass, 

 wax-paper, are employed to obtain a figure from the superimposed sections. 

 Under some circumstances the camera lucida may be used to draw succes- 

 sive sections on the same paper. For surface construction, longitudinal 

 sections are the most suitable. 



In serial construction the reproduction of the object is easily obtained 

 by the aid of the definition lines, which are made in every drawing of a 

 section in the same position as far as regards the definition surface, but 

 which will of course vary in reference to the parts of the object (cf. figs. 152 

 and 153, ef, g Ji). Axial revolution of the object renders reconstruction more 

 complicated ; in this case it is unavoidably necessary to draw a circle with 

 the same radius in each section, so that its position in relation to the 

 definition surfaces shall remain the same for every drawing (figs. 152 and 

 153). Hence the position of the various organs of the object which lie in a 



* Arch. f. Auat. u. Physiol.— Anat. AbtheiJ., 1886, pp. 388-94 (1 pi.). 



