ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



843 



New Method for the Bacteriological Examination of Air.* — The 

 microbiometer of Dr. E. Forstettcr cousists essentially of a U-sbai^ed 

 glass tube (fig. 116) E E, at one end of which is a largish bulb M. The 

 latter is connected by a short neck with a test-tube B, the inferior 

 extremity G of which is made bulbous in order to contain a sufficient 

 quantity of gelatin. C is the aperture of entrance, and B that of exit. 



Into the U-shaped tube is introduced about 10 com. of distilled 

 water E E, and into the bulb G 15 ccm. of 12 per cent, nutrient 

 gelatin. The apertures having been plugged with cotton wool, the 

 apjmratus is sterilized in the usual manner. When required for analysis 

 the plug is removed from C and the aspirator fitted in B, and air drawn 

 through at the rate of about 10 litres an hour. The experiment over, the 



Fw. 117. 



orifices are replugged, and then the gelatin melted by the aid of very 

 gentle heat. The instrument is then placed in the horizontal position, 

 fig. 117, so that the water and gelatin mix together in the bulb M. When 

 thoroughly mixed, the fluid is disj)ersed over plates for the cultivation 

 of this organism. The removal of the gelatin mixture is easily effected 

 through the opening B. 



The aspirator employed by the author is a portable one capable of 

 drawing in 20 litres of air an hour. It consists of a clockwork arrange- 

 ment acting on two rubber bellows, shaped like a Chinese lantern. A 

 needle on a dial-plate indicates the quantity of air which has passed 

 through. 



Examining thin Films of Water. f — Mr. F, Hovenden draws attention 

 to the interesting phenomena presented by a thin film of water under 

 the Microscope, The film may be obtained by simply breathing on the 



* Annales de Micrographie, ii, (1889) pp. 5fi7-71 (2 figs.). 



t 18th Ann. Rep, South London Micr. and Nat. Hist. Club, 1889, pp. 10-1. 



