1896.] the Serum of Highly Immunised Animals, 8fc. 



225 



tion deals with the effects produced upon microbes in vitro by the 

 serums of highly immunised animals, even when extremely dilute. 

 This portion of the enquiry has been carried out mainly in the 

 Bacteriological Laboratory of Guy's Hospital. 



1. A remarkable series of effects are produced on an emulsion of 

 actively motile microbes by the addition of minute quantities of potent 

 kinds of serum. 



2. These effects have been observed with the cholera vibrio, a 

 variety of other vibrios, the typhoid bacillus, the Bacillus coli com- 

 munis, and the Bacillus pyocyaneus. 



3. It is highly improbable that the phenomena are limited to the 

 groups and species here named. Further observation is requisite 

 upon other motile, as well as the non-motile bacteria. 



4. The most prominent of the effects thus produced consists of an 

 immediate aggregation of the bacteria into "clumps"; this is com- 

 bined with loss of motility. Marked inhibition of growth also 

 occurs. 



5. The formation" of clumps can be detected readily by the naked 

 eye. Eventually they gravitate to the bottom of the tube containing 

 them. 



6. A " complete action " is obtained when all the clumps settle 

 down, leaving a perfectly clear fluid. The time required for settling 

 varies somewhat with different organisms, as also according to the 

 amount and potency of the serum used. 



7. The least quantity of serum which will give a " complete 

 reaction" in about one hour forms a convenient standard. A highly 

 potent serum will react thus in 1 per cent, solution, which is a con- 

 venient unit. 



8. The more intense the action of the serum the more rapid and 

 the more complete are the changes which ensue. 



9. By means of the intensity of action in varying dilutions, two or 

 more samples of serum, or of freshly drawn blood, may be gauged 

 according to their potency. 



10. Normal serum, and the serum obtained by immunisations with 

 totally unrelated groups of organisms, do not interact upon the unre- 

 lated microbes, so far as present observation shows. 



11. The action of cholera serum upon more or less closely related 

 vibrios may be " complete " or nil. A series of gradations in 

 intensity of reaction has been observed with cholera serum and 

 vibrios of other species, and vice versa. 



12. The action of such serum cannot therefore be regarded as 

 " specific " ; it is better named special or specialised. 



13. The limit of the absolute value of such serum tests for the 

 diagnosis of cholera vibrios has yet to be determined. 



14. All the typhoid bacilli from nineteen different sources hitherto 



