54 



Scientific Proceedings (125) 



23 (1983) 



Study of bacterial toxins by means of the isolated mammalian 



heart. 



By W. H. MANWARING and WALTER H. BOYD (by invitation) 



[From the Laboratory of Experimental Pathology, Stanford Uni- 

 versity, San Francisco, California] 



The excised rabbit heart is a delicate reacting index of toxic 

 action. It is well suited to the study of bacterial products giving 

 little or no recognizable reaction with intact animals. The tech- 

 nique we have used is the simplified technique proposed by 

 Gunn 1 . The preferable perfusion fluid is Locke's solution con- 

 taining 1 per cent, carefully filtered defibrinated rabbit blood. 

 Control hearts perfused with this mixture beat regularly and 

 strongly for over three hours. With hemolytic or hemagglu- 

 tinating bacterial products this blood mixture, of course, can 

 not be used. With such products, Locke's solution alone may be 

 used, or Locke's solution containing 0.1 per cent, carefully 

 filtered laked blood. Perfused with these solutions, the isolated 

 rabbit heart beats regularly and strongly for over an hour. Il- 

 lustrative cardiac reactions are given below : 



1. End othelio toxin of S. cholerae. Filtrates from broth cul- 

 tures of 5\ cholera are almost non-toxic for the contractile and 

 conducting tissues of the isolated rabbit heart. Minor changes 

 in tone, and in rate and strength of contraction are produced, but 

 the hearts beat regularly and strongly for over ninety minutes. 



Very marked reactions on the capillary endothelium, however, 

 are produced. Within fifteen minutes, the myocardium becomes 

 markedly edematous and markedly hemorrhagic. Histological 

 sections show the tissue spaces widely dilated, and containing 

 numerous extravasated red blood corpuscles. It is believed that 

 this reaction furnishes a valuable method for the study of the 

 immunological adaptations of the capillary endothelium. 



2. Hemagglutinin of Streptococcus hemolyticus: The strep- 

 tococcus was grown in a 10 per cent, dilution of defibrinated 

 rabbit blood in Locke's solution 2 . On testing these filtrates with 



1 J. A. Gunn, Jour. Physiol, 1913, xlvi, 506. 



2 A. H. Clark and L. D. Feliton, J. A. M. A., 1918, lxxi, 1048. 



