234 MEDICAL BACTERIOLOGY 



DILUTION OF BLOOD CELLS 



In performing complement fixation tests, as hereafter described, red blood 

 cells are required. They are procured as described in the preceding chapter 

 and are washed twice. After the second washing a 5 per cent, suspension is 

 made by mixing each cubic centimeter of red blood cells with 19 cc. of normal 

 salt solution. When red blood cells are to be added to a tube, invariably, i cc. 

 of a 5 per cent, suspension is the amount added. To avoid cumbersome ex- 

 pression, the term "red cells" will hereafter be used in this volume to designate 

 i cc. of a 5 per cent, suspension of red blood cells in normal salt solution. 



COMPLEMENT AND AMBOCEPTOR 



Experiment No. 1. Take a normal healthy rabbit that has been subjected 

 to no treatment, obtain some blood from it, place this blood in a refrigerator 

 until it clots and serum separates from it. 



Into a number of test-tubes put various amounts of this serum from o.i 

 to 2.0 cc., add red cells to each tube. Shake the tubes to mix their contents. 

 Note their appearance. Place the tubes in an incubator for i or 2 hours, then 

 inspect them and transfer them to a refrigerator; several hours later make a 

 final inspection. 



Before they were placed in the incubator these tubes showed a homogeneous, 

 bright red, opaque fluid and no precipitate. At the end of incubation the ex- 

 treme upper zone of the fluid was clear, colorless and transparent, on the bot- 

 tom of the tubes there was a slight, dark red precipitate and between these two 

 the fluid was still bright red and opaque. At the final inspection a solid, dark 

 red, opaque sediment, about % inch in depth, covered the bottom of the tubes; 

 above this the fluid was clear, colorless and transparent like water; as 62, 

 Fig. i. 



When the serum and cells were mixed in the tubes by shaking, the cells were 

 evenly distributed throughout the fluid, hence the homogeneous, bright red, 

 opaque appearance and absence of sediment. When these tubes had stood at 

 rest for an hour or two in the incubator the cells gradually precipitated; the pre- 

 cipitation being only partial, but a slight zone at the top of the fluid was entirely 

 free of cells, hence only this slight zone was clear, colorless, and transparent 

 like water, and only a slight sediment was visible at the bottom of the tubes. 



When the tubes were finally inspected, after standing at rest in the incubator 

 and ice box for from 4 to 6 hours, sufficient time had elapsed for precipitation to 

 be complete, in which case all the cells were on the bottom of the tube; all the 

 fluid being free of cells consequently had the appearance of water. 



The above experiment furnishes visible evidence that fresh, unheated serum 

 from a normal untreated rabbit has no effect on red blood cells whether they 

 be obtained from a man, sheep or ox.* This is referred to as no hemolytic 

 effect or no hemolysis. 



* Rabbit serum may occasionally contain natural Hemolysin for foreign red cells. 



