ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 349 



a brass plate C with a notch to receive the binding screw, and also 

 with a cavity for the admission of the knife blade. 



The principal merit of the knife is that owing to the shortness of 

 its blade, it may be easily sharpened by the owner. In order to do 

 this a wooden grip must be fitted to the handle. 



Ordinary v. Serial Sections.* — A writer in ' Nature ' notices 

 with regret a tendency " in certain histological schools to neglect 

 almost entirely the older and simpler methods of cutting sections. 

 Serial section cutting is now such an important item in all morpho- 

 logical work, that it is apt to be used to the exclusion of the older 

 methods which give in many cases undoubtedly better histological 

 results." 



Serial Sections of Celloidin Preparations of Central Nervous 

 System.f — Prof. C. Weigert gives an account of a method devised by 

 him for obtaining a succession of sections, specially adapted for the 

 nervous system. The course of procedure is, he says, so very con- 

 venient that he can recommend it even when a series of sections is 

 not required. 



The process is completed in six steps, of which the first consists 

 in preparing the glass plates. These of course may be of various 

 sizes ; for large preparations, Koch's culture plates may be used, while 

 for spinal cord a plate 4 cm. broad and 15 cm. long suffices. After 

 being cleaned, the plate is covered with a thin layer of celloidin, 

 exactly as a photographer makes a moist plate. It is then set on 

 end and dried. 



The second step is to make the sections and arrange them riband- 

 wise on strips of transparent porous paper. In order to withstand 

 stretching when damp, tenacity is a necessary quality of the paper. 

 The width of the strips should be about double that of the sections. 

 The sections are then disposed in a suitable position along the strips 

 by carefully removing them with a brush from the knife. It is 

 important to keep the strips, when covered with sections, moist while 

 their successors are being cut and arranged. This is accomplished 

 by laying them on blotting paper placed in a dish containing some 

 spirit. 



The third step is to transfer the sections to the celloidin plate. 

 The strips, section side downwards, are laid upon the celloidin 

 surface just sufficiently moistened, the paper surface is softly pressed 

 and then peeled off. Any superfluous fluid is removed with blotting- 

 paper, but anything like dryness of the sections must be avoided as it 

 is injurious to the after steps of the process, which must be im- 

 mediately proceeded with. Not more than one or two strips should 

 be transferred to the same plate. 



The fourth step consists in covering the sections with a thin and 

 even layer of celloidin. When dry the celloidin may be marked (for 

 recognition of series) with a brush dipped in methyl-blue. 



Staining is the next step : immersed in hsematoxylin, the celloidin 



* Nature, xxxiii. (1886) p. 243. 



t Zeitscbr. f. Wiss. Mikr., ii. (1885) pp. 490-5. 



