<)70 SUMMARY OP CURRENT RESEARCHES RELATING TO 



observation of unstained and stained bacteria. Considerable space is 

 devoted to tbo metbods of staining tbc bacillus of tuberculosis, and 

 especially its spores. Tbc mctbod of treating sections of tissue for 

 tbc purpose of showing bacteria, and the various culture methods and 

 materials arc given ; and something is said of saprophytic and parasitic 

 bacteria. The work is illustrated by good woodcuts and two litho- 

 graphic plates. 



MICROSCOPY, 

 a. Instruments, Accessories, &c.* 



Watson-Crossley Microscope. — This (fig. 113) is a combination 

 of the Oblique Illumination Microscope of Messrs. Watson (see 

 this Journal, Vol. I., 1881, p. 51G) and the Swinging Tail-piece 

 Microscope with illuminating prisms, of Mr. E. Crossley (ibid., 

 p. G53). 



The peculiarity of the former instrument, it will be remembered, 

 consisted in the body-tube being set laterally on the limb, the 

 latter being made to incline with the stage, on a horizontal axis in a 

 line with the object, the mirror remaining fixed. By this means, and 

 by the power of rotating the whole instrument round the mirror, 

 illumination in all altitudes and azimuths could be obtained, without 

 moving tbo eye, the light from the mirror remaining constantly upon 

 the object. 



The second instrument was provided with a hollow swinging tail- 

 piece, enclosing three prisms, by which the light from the lamp 

 passing into the hollow trunnion axis was projected down the arm and 

 thence upon the mirror ; thus no change of the Microscope on its 

 horizontal axis affected the illumination which remained constantly on 

 the object. 



The speciality of the new form consists in the above two ideas 

 being combined. It would be difficult to do this if the tail-piece 

 were retained in its ordinary place, as the one form requires much 

 solidity in the axis on which the limb inclines, while the other 

 necessitates the axis being made hollow. The swinging tail-piece 

 with the substage and mirror is therefore separated from the Micro- 

 scope and attached to a pillar on the opposite side of the base. As in 

 the first-mentioned form, the mirror (detached from the tail-piece) 

 can be fixed to the base. The stage also inclines on its axis as well 

 as the limb with the body-tube. 



Thus the observer has the choice of obtaining oblique light in 

 one and the same instrument, either (1) by inclining the body-tube 

 over the fixed mirror, or (2) by using the mirror on the swinging 

 tail-piece. 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; 

 (3) Illuminating Apparatus ; (4) Other Accessories ; (5) Photo-micrography ; 

 (G) Manipulation ; (7) Microscopical Optics, Books, and Miscellaneous matters. 



