EXAMINATION OF WATER FOR MICRO-ORGANISMS 63 



the broken neck of the vessel must of course be sealed 

 in a flame. 



In all cases as short an mterval as possible should 

 elapse between the collection of the sample and its 

 subsequent examination, and during any such interval 

 the water should be placed in as cool a place as pos- 

 sible, or it may be packed in a box surrounded with 

 ice and so forwarded to its destination. The arrival of 

 a sample when sent by train should be advised before- 

 hand if possible, so that any delay in its delivery may be 

 avoided. It is, however, far preferable for the operator 

 to make the cultivations on the spot, and thus avoid all 

 risk of multiplication during transit. 



Special culture media employed. — In order to ascer- 

 tain the bacterial contents of any given water for 

 general purposes, it is obviously of importance that 

 those culture media permitting of the development of 

 the largest number of micro-organisms should be em- 

 ployed. In the case of those waters in which special 

 points require investigation, e.g. in examining for the 

 presence of the typhoid bacillus, &c., we shall indicate 

 later on (see p. 267) what are the particular methods 

 in use ; we shall also have to consider the bacterio- 

 logical examination of waters used for brewing pur- 

 poses, and the special modifications which are then 

 adopted. But it will be convenient, in the first instance, 

 to point out certain modifications in the composition of 

 the ordinary gelatine-peptone medium (the preparation 

 of which has been described on p. 9) which have been 

 found to influence the number of colonies making their 

 appearance on the plate- cultivations of waters. 



Some interesting experiments have been made in 

 this connection by Eeinsch,^ on the addition of different 



^ ' Zur bakteriologischen Untersuchung des TriukwaBsers,' Central- 

 Matt fiir Bahteriologie, vol. x., 1891, p. 415. 



