:{70 H. R. Seddon: 



it usually lies underneath the vein, and a second rather free inci- 

 sion may be necessary. From this the blood spurts or drips freely, 

 and 5 to 10 c.c. can be collected in a test-tube. The blood is allowed 

 to clot, the clot loosened from the sides of the tube for about two- 

 thirds of its attachment, and the tube inverted in a conical urine 

 test-glass. After allowing this to stand for some hours, the serum 

 may be collected free from corpuscles. 



Guinea-pigs. — The following method has been found satisfactory 

 for obtaining small. quantities of serum for diagnostic purposes: — 



Centrifuge tubes are put up, containing 2 c.c. of citrated carbol 

 saline (Sod. chlor. 0.85, Sod. cit. 1, Ac. Carb. liq. 0.5, water 100). 

 The margin of the ear of the guinea-pig is then incised with the 

 scissors and held dependant. There is a .small artery in this region 

 from which, if it has been cut, the blood drips freely. Six drops 

 of blood are collected in the prepared tubes. If we assume that 

 six drops of blood are equal to 0.3 c.c, then we should have about 

 0.2 c.c. of serum in each tube, or a dilution of 1 in 10. 



The tubes are shaken, centrifugalised, and the supernatant fluid 

 pipetted off and tested in various quantities. Though not quite 

 accurate, this method is sufficiently so for determining whether 

 the animal is harbouring the bacilli, as, for example, those animals 

 inoculated with vaginal exudate or milk fiom suspected cows. 

 Healthy, non-inoculated guinea-pigs have invariably given a nega- 

 tive reaction, even with 0.1 c.c. of pure serum (?'.<?., 1 c.c. of the 

 citrated saline mixture), whereas some of our reacting guinea-pigs 

 have given an agglutinating titre of 0.005 c.c, and in one cas© 

 of 0.0005 c.c 



E.ra/ni/iafioii of the Blood of Steers. 



Because of the large number of cows which give a positive 

 agglutination reaction it is important to determine whether agglu- 

 tination of the Contagious Abortion bacillus is brought about by 

 normal ox serum, and, if at all, to what extent. With a view to 

 obtaining information on this point, experiments have been con- 

 ducted Avith the serum of male animals never used for breeding. 



The following experiments have been made with the serum of 

 steers. The animals were for human consumption, and the blood 

 was taken, immediately upon slaughter at the abattoirs, into 

 a bottle containing a small quantity of strong (20%) citrate solu- 

 tion. The serum was obtained by centrifugalising and tested as 

 follows : — 



