768 EECORD OF CURRENT RESEARCHES RELATING TO 



as tlie plate is thicker. He accordingly arranges a layer of liquid 

 between the objective and the eye-piece, the tube which carries the 

 eye-piece being closed by a piece of glass, above which is a small tube 

 communicating with a syringe full of water. On pushing the piston, 

 water is injected between the objective and the eye-piece, and it is 

 thus possible to vary the thickness of the layer of water to the extent 

 of the whole distance which separates the two. 



The method enables thicker cover-glasses to be used, and is 

 available with the most powerful immersion objective, in which it 

 differs from the arrangement of M. Govi (who placed a horizontal 

 glass vessel of water between the object and the objective, and varied 

 the thickness of the layer of water), that being only applicable to 

 Microscopes which have a focal distance of at least 1*01. 



The method may also be very conveniently used, according to the 

 inventor, for photography, as coloured solutions may be employed to 

 give monochromatic light. 



Roy Microtome.* — The woodcut (Fig. 4) represents this instru- 

 ment in natural size, the design of Dr. C. S. Roy. The object aimed 

 at is simply to combine the accuracy gained by the use of a good 

 microtome with the simplicity and convenience with which sections 

 can be cut with the unsupported razor, not a few of the best his- 

 tologists having abandoned microtomes on account of the trouble and 

 waste of time occasioned, more especially in pathological work when 

 a few sections are requii-ed from each of several different specimens, 

 or from different parts of the same specimen. 



The horse-shoe shaped piece of glass rod a is intended to support 

 and guide the knife or razor which is used for cutting, and which 

 glides on the surface turned in the figure towards the observer. This 

 glass rod is firmly fixed by its two extremities in the brass plate 

 5. The smaller brass plate c, on the upper siu-face of which a 

 thin layer of cork is cemented, can be moved forward or backward by 

 the fine-threaded screw d, movement in any direction being prevented 

 by the form of the bed which has been cut in the larger plate for its 

 reception. The small thumb-screw e serves to connect the movable 

 plate with the end of the larger screw d, and admits of the plate 

 being removed when desired. 



Fastened underneath the larger plate in such a way that it can be 

 readily removed and replaced is the bent brass tube /, which is 

 intended to admit of a few drops or of a constant flow of sj)irit being 

 projected on the knife and specimen while sections are being cut. 

 This tube is connected with a test-tube arranged after the principle of 

 a Wolff's bottle, and which can conveniently be suspended by a thread 

 from the button-hole. A caoutchouc tube, with a mouthpiece of glass 

 attached to it, permits of air being blown into the test-tube, forcing 

 out a part of the contained spirit or water by the tube /. 



The method of using the instrument is exceedingly simi)le. The 



portion of tissue to be cut is imbedded in an appropriate imbedding 



mass, and is then placed upon the movable plate c. Upon this it is 



held fixed by the thumb of the left hand, the index and middle fingers 



* ' Journ. Physiol.' (Foster), ii. (1879) p. 19. 



