986 SUMMARY OF CURRENT RESEARCHES RELATING TO 



objective. The writer came near ruining a valuable objective in this 

 way. The solution is also a violent poison, and if the slightest drop 

 touches a tender portion of the skin, as the lips for instance, it burns 

 like fire, and leaves a bad blister. 



Phosphorus mounts, too, are fraught with considerable danger. 

 The beautiful slides of Moller mounted in this medium are evidently- 

 prepared with great care, but after a time the medium either acts 

 upon the asphalt ring or penetrates it, so that the smell of phosphorus 

 is plainly discernible, and in the dark the ring is luminous. A 

 correspondent states that he had a bad fire in his cabinet from the 

 spontaneous combustion of one of these mounts. For those who 

 possess valuable cabinets it will be at least a wise precaution to avoid 

 placing phosphorus mounts with their other slides. They should be 

 kept in a cool, dark place, and in such a locality that other property 

 will not be jeopardized if spontaneous combustion should ensue. 

 Notwithstanding its very high index of refraction, it is not likely 

 that phosphorus will ever become a general favourite as a mounting 

 medium, partly on account of the danger in manipulating it, and 

 partly because the preparations lack permanence, for even when care- 

 fully kept away from the light they deteriorate in the course of 

 time."* 



The statement of the correspondent as to the " bad fire " in his 

 cabiaet through the combustion of a phosphorus-mounted slide is, we 

 fear, a little imaginative, or at least exaggerated, having regard to the 

 very small quantity of phosphorus in a mount. 



Chapman's Slide Centerer.f — This is a device of Mr. A. B. 

 Chapman for mounting objects accurately in the centre of the glass 

 slip, and for applying the thin cover-glass concentrically with the 

 object. It has two revolving backgrounds to contrast with the colour 

 of the object, one being black with white circles, the other white with 

 black circles, and so arranged that, by simply turning a little knob, 

 either can be used or both removed as desired without touching the 

 slip, which can be finished entirely (except the ringing) before it is 

 taken off the instrument. It is so simple that there is nothing to 

 prevent any manipulation required in mounting the object. 



Indian Ink for examining Microscopic Organisms. J — L. Errera, 

 after some general remarks on the principles involved in mounting in 

 media of different refractive indices and in staining,§ points out that 

 living organisms do not absorb the various colouring solutions. The 

 exception to this rule pointed out by Brandt || and Certes ^ are only 

 apparent exceptions. According to Brandt, the nucleus of living 

 Protozoa can be dyed pale violet by a dilute solution of haema- 

 toxylin, and the fatty granules can be dyed brown by Bismarck brown. 



* As to this, see this Journal, atite, p. 475. 

 t Sci.-Gossip, 1884, p. 260. 

 X Bull. Soc. Belg. Micr., x. (1884) pp. 184-8. 



§ "In visiting the laboratories of microscopists one might often believe oneself 

 i,o be in a dyer's workshop." 



11 See this Journal, i. (1881) p. 956. 

 «| Ibid., pp, 527 and 694. 



