32 



Colonel Sir Almroth E. Wright 



[March 9, 



about say one-third of an inch from the tip. We now aspirate a 

 little pus into the stem, drawing it up only as far as our fiducial 

 mark, and blowing it out again leave a wash of pus upon the walls. 

 This done, we sterilize the tip of the pipette, and then aspirate into 

 the stem a series of unit- volumes of serum, 

 dividing each volume off from the next 

 by a bubble of air. The pipette when 

 filled in this manner presents the ap- 

 pearance shown in Fig. 1 ; and we have in 

 the proximal end our first and heaviest 

 implantation of pus, and in the distal end 

 our last and hghtest implantation. The 

 pipette is now placed in the incubator to 

 allow every microbe which is capable of 

 growino^ in serum to do so. After an in- 

 terval of six or more hours we proceed to 

 our examination. What we do is to blow 

 out our series of unit-volumes of serum in 

 separate drops and examine under the micro- 

 scope ; or, better, wx plant out a sample of 

 each drop upon a separate seed-bed. Here 

 in B and C you have the results of such 

 culture represented diagrammatically — the 

 meagre crop in B being that obtained with 

 the patient's serum, and the more copious 

 crop in C being that obtained with normal 

 serum. 



And you have in the next figure (Fig. 2) 

 a drawing of an agar tube implanted from 

 a pyo-sero-culture made with the serum of 

 a wounded man. In the upper part of the 

 agar tube you have two seed-plots implanted 

 from the distal portion of the capillary stem. 

 These have remained sterile. In the middle 

 of the tube you see four plots implanted 

 from the unit-volumes of serum which 

 occupied the middle region of the capillary 

 stem. These have grown colonies of only 

 one species of microbe — the streptococcus. 

 At the bottom of the tube you see seed-plots 

 implanted from tlie proximal end of the 

 capillary stem. These are overgrown with 

 colonies of staphylococcus. But no doubt 

 interspersed with and overgrown by these are also colonies of strepto- 

 cocci. If, instead of cultures from the patient's serum, I had been 

 showing you here cultures from normal serum, what you would have 

 seen would have been a much larger number of fertile seed-plots, and 



^ Fig. 2. — A portion of a 

 pyo-sero-culture planted 

 out upon an agar slant 

 divided up by furrows 

 into a series of seed- 

 beds. 



