74 METHODS OF CULTIVATION OF BACTERIA. 



received in a sterile test-tube. Several cubic centimetres of 

 fluid can thus usually be obtained, no suction being required ; 

 thereafter it can be examined bacteriologically by the usual 

 methods. The depth of the sub-arachnoid space from the sur- 

 face varies from a little over an inch in children to three inches, 

 or even more, in adults the length of the needle must be suited 

 accordingly. In making the puncture it is convenient to have 

 either a sterile syringe attached, or to have the thick end of 

 the needle covered with a pad of sterile wool, which is of course 

 removed at once when the fluid begins to flow. 



The Bacteriological Examination of Urine. In such an 

 examination care must be taken to prevent the contamination 

 of the urine by extraneous organisms. In the male it is usually 

 sufficient to wash thoroughly the glans penis and the meatus 

 with i-iooo corrosive sublimate the tips of the meatus being 

 everted for more thorough cleansing. The urine is then passed 

 into a series of sterile flasks, the first of which is rejected in 

 case contamination has occurred. In the female, after similar 

 precautions as regards external cleansing, the catheter must be 

 used. The latter must be boiled for half an hour, and anointed 

 with olive oil sterilised by half an hour's exposure in a plugged 

 flask to a temperature of 120 C. Here, again, it is well to 

 reject the urine first passed. It is often advisable to allow the 

 urine to stand in a cool place for some hours, to then withdraw 

 the lower portion with a sterile pipette, to centrif ugalise this, and 

 to use the urine in the lower parts of the centrifuge tubes for 

 microscopic examination or culture. 



Filtration of Cultures. For many purposes it is necessary 

 to filter all the organisms from fluids in which they may have 

 been growing. This is especially done in obtaining the soluble 

 toxic products of bacteria. The only filter capable of keeping 

 back such minute bodies as bacteria is that formed from a tube 

 of unglazed porcelain as introduced by Chamberland. The 

 efficiency of such a filter depends on the fineness of the grain 

 of the clay from which it is made ; the finest is the Kitasato filter 

 and the Chamberland " B " pattern ; the next finest is the 

 Chamberland " F " pattern, which is quite good enough for 

 ordinary work. There are several filters, differing slightly in 

 detail, all possessing the common principle. Sometimes the 

 fluid is forced through the porcelain tube. In one form the 



