ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 257 



alcohol here is the essential reagent, but the eosin provides a red 

 counter-stain. The preparation is then washed, cleared and mounted 

 in the usual way. 



Fixing and Staining Toxoplasma.* — H. G. Plimmer found these 

 parasites in the blood of the general and in that of the pulmonary 

 circulation, and also in the liver, of animals kept in the Zoological 

 Gardens. Most of the films were fixed wet in the vapour of iodine 

 dissolved in chloroform, and were stained with Giemsa's stain, made 

 alkaline, and followed by acetene and xylol. Others were fixed by the 

 Carnoy-Lebrun method and stained with Weigert's hsematoxylin, or 

 with alkaline Giemsa stain. 



6. Miscellaneous. 



Demonstrating: Silicious Particles in Lung.f — The nature of the 

 particles of mineral matter which become embedded in the lung-tissue 

 in cases of miner's phthisis has been determined by W. Watkins- 

 Pitchford and J. Moir, by microscopical examination in polarized light 

 of specially prepared sections of silicotic lungs, their results being 

 given in Publication No. VII. of the South African Institute for Medical 

 Research (Johannesburg, 1916). In polarized light the field is sug- 

 gestive of a starlit sky, but in ordinary circumstances only the larger 

 particles are so visible. The particles have the form of irregular and 

 angular, more or less elongated, chips or flakes, the majority being less 

 than 2 fjL in diam., and very rarely reaching as much as 14 /x. The 

 smaller flakes, when lying flat, have not sufficient thickness to react 

 on polarized light, and they are only seen as streaks when they are set 

 edgeways (the light then traversing a longer path through the doubly 

 refracting medium). Further, the particles are obscured by the tissue 

 in which they are embedded. The method previously adopted of de- 

 stroying the lung-tissue by means of hydrochloric acid and potassium 

 chlorate also resulted in the destruction of some of the mineral matter. 

 This objection is overcome by treating the sections with nitric acid or 

 strong hydrobromic acid. Such prepared sections were compared with 

 preparations of the dust collected from the air in the Rand gold mines, 

 and of the powder obtained by finely grinding the rock (" banket ") from 

 these mines. The mineral species identified include quartz (constitut- 

 ing more than 99 p.c. of the particles), sericite-mica, rutile, zircon, and 

 tourmaline, and perhaps chlorite. Similar particles of mineral dust 

 were also detected in the tissue of normal lungs ; for example, the 

 two lungs of a farmer, who had never worked in the mines, were 

 estimated to contain a hundred thousand million particles of foreign 

 mineral matter, whereas in the lungs of a miner affected with the 

 disease the estimate reaches the appalling number of twenty to thirty 

 millions of millions of such particles. 



* Proc. Roy. Sec, Series B, Ixxxix. (1916) pp. 291-6 (10 figs.), 

 t Nature, Jan. 25, 1917, p. 416. 



