i66 



sera lose their property of agglutination, but recover this when 

 cultivated upon the ordinary culture-media. Weil* obtained 

 a culture of typhoid bacillus from an abscess in the thyroid 

 of a typhoid convalescent which did not agglutinate with the 

 patient's serum nor with other homologous sera. 



Agglutination has been found to take place even spontane- 

 ously in cultures. Still, it is, after all, more or less a specific 

 reaction, and is employed as an aid in the diagnosis of typhoid 

 fever, where it is spoken of as the Widal or Gruber-Widal 

 test. Under proper precaution it is valuable in this special 

 case, and will be referred to again in connection with the des- 

 cription of the typhoid bacillus. 



Other bacteria which agglutinate with the homologous sera 

 are: Spirillum of cholera, B. pyocyaneus, B. proteus, B. coli 

 communis. Micrococcus melitensis, B. mallei, B. tuberculosis, 

 Diplococcus pneumonias, B. pestis bubonicae, and B. dysenterias. 

 Trypanosomes also agglutinate with homologous sera. 



Lysins. — There are certain substances found normally 

 present or produced artificially in the blood which have the 

 property of breaking up foreign red blood-cells introduced 

 into the circulation or into the blood-serum outside the body. 

 This is not only true of red blood-cells, but certain bacteria 

 also become broken up when introduced into the blood of 

 certain animals. This process is spoken of as cytolysis, and 

 when occurring in red blood-cells, is called hemolysis; in 

 bacteria, bacteriolysis. The substances causing cytolysis are 

 called lysins. As already stated, lysins for certain foreign 

 cells are normally present in the serum of certain animals; 

 thus, human red blood-cells are disintegrated by sheep's serum, 

 rabbit's blood-serum disintegrates anthrax bacilli, and numer- 

 ous other examples exist of lysin normally present in blood- 

 serum. But whether normally present or not, specific lysins, 

 Hke specific agglutinins, are made to appear in the blood- 



* Weil. Ibid. 



