METHODS OF CULTURE AND OF EXAMINATION. 



99 



employ special culture-dishes, which permit the entrance of 

 hydrogen through two openings in the lid that communicate 

 with a gutter-like excavation of the dish. The lid is fas- 

 tened to the periphery of the dish by means of vaselin, and 

 it is revolved as soon as the vessel is filled with hydrogen, 

 in order that the openings in the lid and the gutter are no 

 longer opposed to one another, and communication with 

 the outside is cut off (Kamen dish). The hydrogen is gen- 

 erated in a Kipp's apparatus (Fig. 30) that is filled with 

 pure zinc and sulphuric acid, and is freed of hydrogen 

 sulphid and of oxygen, by means of two wash-bottles con- 



Fig. 30. Kipp's apparatus for producing hydrogen, with wash-bottles attached 



(Ernst). 



taining an alkaline lead-solution and an alkaline pyrogallic- 

 acid solution. The employment of Kamen's plates is 

 attended with certain difficulties ; especially is it difficult to 

 drive out all of the oxygen. 



In the preparation of anaerobic plates in an atmosphere 

 of hydrogen Botkin's apparatus (Fig. 3 1) is employed. This 

 consists of a large bell-jar, within which, upon a glass stand, 

 plates are exposed free, without a cover. The bell stands 

 upon a lead cross in a large glass dish. Between the mar- 

 gin of the bell and the stand is a space through which 

 passes a U-shaped rubber tu.be for the conduction of the 



