ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 



113 



is not mentioned by Adams in his ' Micrograpliia lUustrata,' 1771, 

 or in his ' Essays on the Microscope,' 1787. Mr. Kitton tried it first 

 with a j-inch objective upon Pleurosigma angulatum, using oblique 

 light from the mirror ; the striae came out very distinctly. On removing 

 the globe, the striae vanished and required a more oblique ray to 

 render them again visible. Tried on Synedra robusta, it resolved the 

 stri^ into beads. With a |- inch, and not altering the previous position 

 of the mirror, a "black field" was obtained. The object Haliomma 

 Humboldtii was seen with beautiful effect, appearing as though 

 illuminated by intense moonlight with a slight green tinge and 

 delightfully cool to the eye. It is also to be recommended with 

 polarized light for softness of tint and impenetrable blackness of field 

 when the prisms are crossed. A globe (6 inches in diameter) should 

 be used, filled with a dilute solution of sulphate of copper (about 

 ^ ounce of saturated solution to 1 pint of water). The mixture must 

 be filtered if ordinary water is used, though the intensity of colour 

 is somewhat a matter of taste. The distance of the globe from the 

 lamp should be about two or three inches ; from the globe to the 

 mirror about eight to twelve inches. 



Stein's small MicrophotograpMc Apparatus* — Fig. 22 shows 

 Stein's microphotographic apparatus which, though small and simple, 

 is said to answer its purpose completely. It 

 is on the plan of Harting's apparatus and 

 consists of a cone F which is inserted into 

 the tube M of the Microscope instead of an 

 eye-piece, a plate of ground-glass is fixed 

 to the top, and on this the image can be 

 focussed, the observer's head being covered 

 with a black cloth. The ground-glass plate 

 is replaced by the prepared sensitive plate 

 and the image can then be readily photo- 

 graphed. 



Ranvier's Myo-Spectroscope. j — In this 

 simple and ingenious instrument (available 

 for rapid superficial demonstrations) a prism 

 is replaced by the muscular tissue, the trans- 

 verse stri83 of the muscular bundles acting on white light like a 

 grating and producing spectra. 



The muscles of the frog are the most suitable for observation, and 

 especially the sartorius muscle, the bundles of which are parallel. 

 The muscle having been taken with care from a living frog, it 

 is dried for some hours in a stove at 40° C, after having been 

 stretched with pins on a piece of cork. The muscle is then planed on 

 both sides with a sharp scalpel, soaked in turpentine, and mounted in 

 Canada balsam. 



Fig. 22. 



* Thanhoffer's 'Das Mikroskop und seiue Anwendung,' 1880, p. -18 (1 fig. 

 t Ranvier's 'Traite techuique d'Histologie,' Paris, 1878-80, pp. ,316 

 (1 fig-)- 



Ser. 2.— Vol. II. I 



19 



