384 EXPERIMENTAL INFECTIONS DURING LIFE 



the column of fluid by maintaining the pressure on the 

 teat, neither relaxing nor increasing it. 



8. Withdraw the point of the pipette clear of the 

 fluid, and again relax the pressure on the teat very 

 slightly. The column of saline solution rises higher in 

 the stem, and a column of air will now enter the pipette 

 and serve as an index to separate the first volume of 

 fluid drawn into the stem from the next succeeding one. 



9. Again introduce the end of the pipette into the 

 fluid and draw up a second volume of saline to the level 

 of the grease pencil mark, and follow this with a second 

 air index. 



10. In like manner take up seven more equal volumes 

 of saline solution and their following air bubbles. 

 There are now nine equal volumes of normal saline in 

 the pipette. 



1 1 . Now pass the point of the pipette into the blood 

 tube and dip the open end below the surface of the 

 serum. Proceeding as before, aspirate a volume of 

 serum into the capillary stem up to the level of the 

 pencil mark. 



12. Eject the contents of the pipette into the small 

 tube marked 10 per cent, by compressing the rubber 

 teat between thumb and finger. 



13. Mix the one volume of serum with the nine 

 volumes of saline solution very thoroughly by re- 

 peatedly drawing up the whole of the fluid into the 

 pipette and driving it out again into the test-tube. 



14. Now take a clean pipette and proceed precisely 

 as before, 4 to 10. 



15. Having aspirated nine equal volumes of saline 

 into this second pipette, now take up one similar 

 volume of the fluid in the " 10 per cent, tube." 



1 6. Eject the contents of this pipette into the second 

 tube marked i per cent, and mix thoroughly as before. 



17. In similar fashion make the o.i per cent, solution 

 and transfer to the third tube. 



