ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 661 



(.4) Photomicrography. 



Observations and Contributions to the Practice of Scientific 

 Photomicrography and Macrophotography inclusive of Colour Photo- 

 graphy with Autochrome Plates.* — M. Wolff has compiled a thorough 

 and complete treatise on the al)ove subject, with especial reference to the 

 requirements of the scientific investigator. The treatise is divided into 

 thirteen sections, and contains numerous statistical tables of such impor- 

 tant matters as time exposures and solutions. 



(6) Miscellaneous. 



Observations on the Brownian Movement, with special reference 

 to the Anthrax Spore.f— E. Emrys-Roberts and 8. B. Walsh, having 

 made the observation that anthrax spores suspended in tap-water exhibit 

 practically no Brownian movement, have endeavoured to investigate the 

 phenomena and incidentally to attempt to elucidate some points in con- 

 nexion with Brownian movement. In their investigations they made 

 use of Staphylococcus aureus and Indian ink granules as controls, on 

 account of their approximate size to anthrax spores, and also because the 

 one could be taken as typical of dead particles and the other of living 

 particles, both exhibiting well-marked Brownian movement. A number 

 of exhaustive experiments showed the practical immobility of anthrax 

 spores under all circumstances, and also that this property was to a 

 certain extent shared by other spores. The experiments did not favour 

 the theory that Brownian movement is an indication of the molecular 

 movement of the suspensory fluid ; but rather that it is due to unequal 

 differences in surface tension between the particles and the suspensory 

 fluid. A reasonable supposition to account for the comparative immo- 

 bility of the anthrax spores is to postulate tiieir possession of an envelope 

 so nearly perfectly uniform that no unequal differences of surface tension 

 exist, and hence no conversion of potential into actual energy. To put 

 this theory to the test, the spores were treated with antiformin and other 

 liquids likely to attack cellular material, and the spores were then found 

 to exhibit marked Brownian movement. It would seem that the treat- 

 ment had so altered the surface of the spores as to bring into action the 

 forces leading to the production of Brownian movement, and this result 

 would appear to strengthen the theory that the movement is due to 

 unequal differences of surface tension between the particles in question 

 and the suspensory fluid. 



Experiments in Scientific Microscopy. | — Under the above title 

 H. Siedentopf has published the first part of what seems intended to be 

 a complete practical guide to the most recent developments in advanced 

 microscopy. This first part embraces sixteen pages and is copiously illus- 

 trated. The experiments dealt with are: — 1. Observation by light- 

 ground illumination. 2. Observation of the same preparation by dark- 



* Zeitschr. wiss. Mikrosk., xxix. (1912) pp. 145-81. 

 t Brit. Med. Journ., 1912, ii. pp. 1305-6. 



X Ubungen zur wiss. Mikrosk., Heft i., Dunkelfeldbeleuchtung. Zusammau- 

 gestelte von H. Siedeutopf mit 20 Piguren ; published by S. Hirzel (Leipzig), 1912. 



