INTRODUCTION 15 



the agglutinating power of ricin on erythrocytes in the 

 presence of its antibody. 1 In this case it is possible 

 to discriminate between different degrees of agglutination 

 and thereby to measure the quantity of free ricin present. 

 This method has been developed chiefly in the Danish 

 serum institute. 2 



The most fruitful application of these researches "in 

 vitro " has been in the study of the haemolysins. 3 The lysin 

 to be investigated is added in different quantities to circa 

 8 c.c. of a suspension of 2 c.c. erythrocytes in 98 c.c. of 

 physiological salt solution. Before the admixture of lysin, 

 water was added to the lysin-solution until its total 

 quantity became 10 c.c. The best method is to add the 

 suspension in an energetic manner so that a well-mixed 

 fluid immediately results. Otherwise the lysin is con- 

 centrated in some parts and is absorbed by the erythrocytes 

 in the proximity, and other erythrocytes remain nearly 

 intact if the shaking takes place even a few seconds 

 (30 to 60) after the mixing. Therefore the usual result is 

 that the haemolysis is less the longer the time intervening 

 between mixing and shaking. (Variations of 50 per cent 

 frequently occur for this reason.) To develop the haemol- 

 ysis, the test-tubes are placed during a certain time, gener- 

 ally one or two hours, in a water-bath or other thermostat 

 at the desired temperature (in most cases 37 C). The 

 haemolysis increases with time and seems to tend to a 

 limit which is reached the more rapidly the more active 



1 Ehrlich : Fortschritte der Medicin, 1897, No - 2 - 



2 Compare Jorgensen and Madsen : Festskrift, VI, 6, Copenhagen, 1902. 



8 Madsen: "Uber Tetanolysin," Zeitschr. f. Hygiene, 32. p. 214 (1899); 

 Arrhenius, Madsen: Festskrift, III, 9, Copenhagen, 1902. 



