io8 GENERAL BACTERIOLOGICAL DIAGNOSIS. 



obtained whole. They may be treated in one of two ways. 

 i. The surface over one part about an inch broad is seared 

 with a cautery heated to dull red heat. All superficial 

 organisms are thus killed. An incision is made in this 

 seared zone with a sterile scalpel, and small quantities of 

 the juice are removed by a platinum loop to make cover- 

 glass preparations and plate or smear cultures. 2. An 

 alternative method is as follows : The surface is sterilised 

 by soaking it well with i to 1000 corrosive sublimate for 

 half an hour. It is then dried, and the capsule of the 

 organ is cut through with a sterile knife, the incision 

 being further deepened by tearing. In this way a perfectly 

 uncontaminated surface is obtained. Hints are often 

 obtained from the clinical history of the case as to what the 

 procedure ought to be in examination. Thus, as a matter 

 of practice, cultures of tubercle and often of glanders bacilli 

 can be easily obtained only by inoculation experiments. 

 Typhoid bacilli need hardly be looked for in the faeces 

 after the first ten days of the disease, and so on. 



Routine Procedure in Bacteriological Examination of 

 Material. In the case of a discharge regarding which 

 nothing is known the following procedure should be 

 adopted: (i) Several cover-glass preparations should be 

 made. One ought to be stained with saturated watery 

 methylene-blue, one with a stain containing a mordant 

 such as Ziehl-Neelsen carbol-fuchsin, one by Gram's method. 

 (2) (a) Gelatine plates should be made and kept at room 

 temperature, (I)) a series of agar plates or successive strokes 

 on agar tubes (p. 62) should be made and incubated at 

 37 C. Method (^) of course gives results more quickly. 

 If microscopic investigation reveals the presence of bacteria, 

 it is well to keep the material in a cool place till next day 

 when if no growth has appeared in the incubated agar some 

 other culture methods (e.g., blood serum or agar smeared 

 with blood) may be applied. If growth has taken place, 

 say in the agar plates, one with about 200 or fewer colonies 

 should be made the chief basis for research. In such a 

 plate the first question to be cleared up is : Do all the 



