THE AGGLVnyiSS. 159 



can be used in making the a^;lntination t^;. They impregnated 

 small bite of sponge with four or five drops of the blood, dlowed to 

 dry, and subsequently macerated the pieces for half an hour in firjm 

 ten to fifteen drops of bouillon. The addition of this extract to 

 bouillon caltores of the !Eberth bacillus induced typical agglutination. 

 Johnston ' first demouBtrated that a drop of blood allowed to dry 

 upon non-absorbent paper may be transported through any distance 

 and kept indefinitely and still be capable, after being mcnstened with 

 water, of giving the a^lutinatian test. In this way this method of 

 making a diagnosis of typhoid Sever has been popol^ized and placed 

 practically within the readi of every physidan. It is safe to say 

 that at present more than 90 per cent, of the a^htination tests made 

 are applied to dried blood stains. The only objection to this me&od 

 is that exactness in dilution can not be secured, and much must de- 

 pend upon the judgment and experience of the individual malring the 

 t^t. However, for clinical purposes, dried blood gives, in a large 

 per cent, of cases, evidence which is of positive value. Usually the 

 blood stain is rubbed up with either sterilized water or physioh^cal 

 salt solution, and this is added to a bouillon culture of the typhoid 

 bacillus twenty-four hours old. A hanging drop of this mixture is 

 prepared and examined under the microscope. The extent to which 

 the blood or serum should be diluted is still a matter about which 

 there is a difference of opinion. The general rule is that the dilu- 

 tion should not be less than 1 to 20 and that agglutination in this 

 dilution should occur within thirty minutes. However, in order 

 to be quite sure concerning the rrault, the dilution should not be less 

 than 1 to 60, and if agglutination occurs in this dilution within thirty 

 minutes, the evidence that the blood has come from an individual 

 with typhoid fever is quite positive. With dilutions of 1 to 30 or 

 less, agglutination is frequently obtained with normal serum, and 

 more frequently given in certain diseases such as tuberculosis, pneu- 

 monia, septicemia, and influenza. When a^lutination does not 

 occur in the dilution of 1 to 60, but is observed in the dilution of 1 

 to 30 the weight of evidence is in favor of the existence of typhoid 

 fever, but the proof cannot be considered as positive. In this, as in 

 the application of many other clinical tests, much depends upon the 

 skill, experience and good judgment of the observer. It appears 

 that about 96 per cent, of the cases of typhoid fever furnish some 

 time during the course of the disease a serum which will give this 

 reaction. It will be seen from this that &ilure to secure the a^lu- 

 tination test is not absolute proof of the non-existence of typhoid 

 fever. Experience has shown that attenuated cultures are better 

 suited for the a^lutination t^t than more virulent ones. However, 

 the evidence on this point is by no means unanimous, and an explana- 

 tion is not easily given. Young cultures are better than older ones, 

 ■ New York Med. Journal, 44, 1896. 



