164 Scientific Proceedings, Royal Dublin Society. 



importance that these substances should be as nearly colourless as 

 may be, and the best way to arrive at this result in the case of 

 gelatine, seems to be to shorten the period of boiling as much as 

 possible, after the addition of the peptone during the preparation 

 of the medium. To obtain a clear agar-agar has at all times been 

 a difficult matter, and I do not purpose entering here upon the 

 various plans in vogue in different laboratories ; they are well 

 known to practical men who take in the German " Centralblatter " 

 which are devoted to bacteriology. The selection of a tube so 

 flattened as to contain but a thin layer of the substratum will, 

 even with an indifferent agar, ensure sufficient transparency, pro- 

 vided the specimen, when finished off, be placed in a favourable 

 illumination. After the liquid medium has been placed in these 

 flattened tubes, the cotton- wool plug, with which of course they 

 have been provided, and which, together with the tube, has been 

 sterilised with dry heat (180° 0. for twenty minutes), is replaced, 

 and the tube with its contents is sterilised in a current of steam for 

 ten minutes on three consecutive days, and is then ready for 

 inoculation. This is accomplished by means of the usual thrust 

 or stab procedure, and in order that success be achieved — in other 

 words, that a perfectly typical culture be the result — it is necessary 

 to pay attention to two points : the inoculating needle must be of 

 stiff platinum wire, so as not to bend in the process, and so as to 

 give a perfectly straight inoculation channel ; and the number 

 of germs introduced must be small. If a bouillon-culture be 

 employed as the germ-source, it is well to have a series of drops of 

 sterilised water ready, and having introduced a minute quantity of 

 the bouillon into the first, inoculate the second from it, and so on, 

 A previous check experiment will show the degree to which the 

 dilution ought to be carried. After inoculation the tube is set 

 aside to develop under suitable conditions of temperature, light- 

 access, &c. ; and lastly, when a perfectly typical development has 

 taken place, the upper part of the tube is hermetically closed, by 

 fusion of the glass at the blowpipe flame. 



I will now show a few examples of pathogenic organisms cul- 

 tivated in this manner. 



The JDijjlococcus 2^nenmomm of Frankel, of which I show you a 

 tube, grows along the inociilation track in the form of small, white, 

 perfectly discrete granules. The surface growth is but slight. 



