116 



METHODS OF EXAMINING SERUM 



110 further. A mark is made on the tube at the proximal end of the 

 mercury, which is now allowed to run out, aud the tube is carefully cut 

 through at the mark. A piece of ordinary quill tubing is drawn out and 

 broken off just below the point where narrowing has begun, the hair end 

 of the capillary tube is slipped through the broken-off end, and the tube 

 is fixed in position with wax as shown in the figure. A rubber nipple 

 placed on the end of the pipette completes the 

 apparatus. If by pressing the nipple the air be 

 expelled from the pipette, and the end dipped 

 under mercury, exactly 5 c.mni. will be taken 

 up when pressure on the nipple is relaxed. 

 Thus other tubes can be very readily calibrated 

 by the mercury being expelled into them, and its 

 limits marked on their bores. 



For measuring equal parts of different 

 fluids, the pipette shown in Fig. 40, d, 

 in connection with agglutination is very 

 useful. 



Methods of testing for Simple Ag- 

 glutination. — By agglutination is meant 

 the aggregation into clumps of uniformly 

 disposed bacteria in a fluid ; by sediinenta- 

 tion the formation of a deposit composed 

 of such clumps when the fluid is allowed 

 to stand. Sedimentation is thus the 

 naked-eye evidence of agglutination. The 

 blood serum may acquire this clumping 

 power towards a particular organism under 



FlG '™™ 9, -. Wr t i ght ' s / certain conditions,— these being chiefly met 

 c.mm. pipette. A, . . ' . o _ J 



casing of quill tubing ; with when the individual is suffering from 

 B, rubber nipple ; C, the disease produced by the organism, or 

 rpmlTtabe of F 5 has recovered from it, or when a certain 

 c.mm. capacity ; D to degree of immunity has been produced 

 E, hair capillary. artificially by injections of the organism. 



The nature of this property will be dis- 

 cussed later. Here we shall only give the technique by which 

 the presence or absence of the property may be tested. There 

 are two chief methods, a microscopic and a naked-eye, corre- 

 sponding to the effects mentioned above. In both, the essential 

 process is the bringing of the diluted serum' into contact 

 with the bacteria uniformly disposed in a fluid. In the 

 former this is done on a glass slide, and the result is watched 

 under the microscope ; the occurrence of the phenomenon is 

 shown by the aggregation of the bacteria into clumps, and if the 

 organism is motile this change is preceded or accompanied by 

 more or less complete loss of motility. In the latter method 



