SERUM 47 



Modification recommended. A better yield of serum is obtained if instead of 

 collecting the blood in glass dishes Latapie's apparatus be used (p. 50). For the 

 present purpose the tube a (fig. 40) is replaced by a sterile funnel by means of which 

 the blood is collected as it spurts from the severed vessel. When the bottle is half- 

 filled, the funnel is taken out and an india-rubber plug put in its place. The further 

 steps are described at p. 50. 



The serum is sterilized in the following manner : 



4. Take the Chamberland flasks containing the serum to the laboratory. 

 In spite of the precautions taken the serum will be certain to be more or 

 less contaminated, and must therefore be sterilized. Distribute it first into 

 flasks with long necks thus : flame the mouth of the flask in a Bunsen burner 

 and remove the cotton-wool plug : break off the capillary point of the tubulure 

 on the Chamberland flask, pass the broken end through the flame, and intro- 

 duce it some distance into the neck of the other flask ; then by blowing 

 through the tube B the serum can be transferred to the other flask. Mean- 

 while the wool plug of this flask is held between the thumb and index finger 

 of the left hand. 



5. The flask being about three-parts filled, its wool plug is removed and 

 the neck heated in the blow-pipe and sealed a few centimetres from the 

 bulb. As many flasks are used as are necessary to contain the serum collected. 



6. The flasks after filling and sealing are heated in a water bath, as already 

 described (p. 12), to 56 or 58 C. for one hour on eight consecutive days. 



7. When sterilized the serum has to be distributed. A mark is made on 

 the neck of the flask with a glass cutter near the sealed end and to this scratch 

 the end of a very hot glass rod is applied : 



this cracks the glass and the crack is ex- 

 tended by touching the end of it with the 

 heated glass rod. The two ends of the 

 fracture soon join, and with a gentle tap 

 the end of the neck which was sealed in the 

 flame can be easily separated and the flask 

 opened. 



Place the flask B on a cork ring E so that 

 the neck is as nearly horizontal as possible. 



Flame the pointed tubulure of a sterile 

 Chamberland flask A in a Bunsen, break off 

 the end with sterile forceps and insert the 

 tube into the flask so as to almost touch 

 the clot D, and aspirate the serum C. 

 Discard the top layer of serum because 



having been in contact with the air, it may FIG 36. Distribution of serum, 

 possibly be contaminated by dust (fig. 36). 



8. By means of the Chamberland flask, distribute the serum in sterile tubes, 

 passing the mouth of each tube rapidly through the flame before taking out 

 the wool plug, and flaming also the pointed tubulure of the Chamberland. 

 Pass the tapering end well into the test-tube, and pour about 10 c.c. into each. 

 Replace the plug in the tube. 



The serum is now ready either for coagulation or for use in the liquid state 

 (in the latter case it should be first incubated for 48 hours at 30 C.). 



If the serum is to be set this should be done as soon as possible, for should 

 any organisms have gained access to the tubes during filling, the heat of 

 coagulation will very probably destroy them. 



Note. The serum may be sterilized by filtration instead of by heat ; but filtra- 

 tion of 'serum is a long and tedious operation, and usually a troublesome one, as the 



