THE AGGLUTININS. 155 



ganism. The serum of men who have never had typhoid fever 

 may, when the dilution is not greater than one to ten, agglutinate 

 the Eberth bacillus, and it should be remarked that the manifesta- 

 tion of this property by the sera of different individuals varies 

 within wide limits. It is still a question whether the agglutinating 

 action manifested in the serum of immunized animals, or that of 

 persons sick with typhoid fever, is due to an exaggeration of a nor- 

 mal property, or is caused by the presence of a new substance. 



The period in the course of typhoid fever when marked aggluti- 

 nation is first manifested by the serum varies widely in different 

 cases. As a rule, agglutination in a weU-marked form is not ob- 

 tained until after the seventh day, but there are cases on record in 

 which it- has been obtained as early as the second day, and there are 

 others in which it has been delayed until the second, third, and even 

 fourth week. Likewise the disappearance of the specific agglu- 

 tinating property from the serum after recovery from typhoid fever 

 is very variable in time. The reaction has been known to fail ten 

 days after the establishment of apyrexia, while in other instances 

 marked agglutination has been secured many years after recovery 

 from typhoid fever. The intensity of the reaction varies widely, 

 and is not always in proportion to the severity of the disease. 

 Many methods of measuring the agglutinative power of sera have 

 been proposed. One recommended by Widal and Sicard we have 

 found to be satisfactory. A number of tubes containing each one, 

 two, three, four, five, etc., c.c. of bouillon are kept on hand. When 

 a test is to be made, one adds a drop of the serum to each of these 

 tubes and then inoculates the tube with a typhoid culture. The 

 tubes thus prepared are placed in the incubator and kept at 37° for 

 from four to six hours. At the expiration of this time it may be 

 seen at a glance in which tubes agglutination has occurred, inasmuch 

 as the contents of these tubes will be unclouded and the bacilli will 

 be found deposited on the bottom. If this reaction does not take 

 place in tube number one, which represents a dilution of 1 to 20, 

 the test is considered as wholly negative. If number three contains 

 clumps, while number four is uniformly clouded, the serum is active 

 in the proportion of one to sixty and inactive in the proportion of 

 one to eighty. An absolute determination of the agglutinating 

 property of a given serum is probably not within the range of pos- 

 sibility, and we indicate the relative activity of different sera by the 

 dilutions in which the reactions are observable. The number of 

 germs present certainly has some influence, and it is a well-known 

 fact that the age of the culture is of importance in making this test. 

 In young cultures the bacilli are more motile, and there is less tend- 

 ency to manifest the phenomenon of pseudo-agglutination. 



Agglutinins exist not only in the blood, but in other fluids of the 

 body. The manifestation of agglutinating power by the urine is in 



