74 METHODS OF CULTIVATION OF BACTERIA 



considerable pressure is necessary, it is evident it must be put 

 on a pipe leading directly from the main. Sometimes, when 



fluids to be filtered are 

 very albuminous, they 

 are forced through a 

 , porcelaih$?cylinder by 

 compressed carbonic 

 acid gas. The filtra- 

 tion of albuminous 

 fluids may sometimes 

 be facilitated by keep- 

 ing them near blood- 

 heat during the pro- 

 cess. For ordinary 

 bacteriological work, 

 filters of various kinds 

 are in the market 

 (such as those of Klein 

 and others), but the 

 most generally -con- 

 venient is that in 

 Pig. 26. — Geissler's vacuum pump arranged with which the fluid is 

 manometer for filtering cultures. (The tap k d tislaa gh the 

 and pump are intentionally drawn to a larger 6 , 



scale than the manometer board to show porcelain by exnaust- 

 details.) j n g the air in the 



receptacle ,into which 

 it is to flow. This is conveniently done by means of a 

 Geissler's water-exhaust pump (Fig. 26, g), which must be 

 fixed to a tap leading directly from the main. The connection 

 with the tap must be effected by 

 means of a piece of thick-walled 

 rubber-tubing as short as possible, 

 wired on to tap and pump, and 

 firmly lashed externally with many 

 turns of strong tape. Before lash- 

 ing with the tape the tube may be 

 strengthened by fixing round it 

 with rubber solution strips of the 

 rubbered canvas used for mending 

 punctures in the outer case of a Fig. 27.— Chamberland's candle 

 bicycle tyre. A manometer tube ™* flask arranged for ftltra " 

 (6) and a receptacle (c) (the latter 



to catch any back flow of water from the pump which may 

 accidentally occur) are intercepted between the filter and' the 



