METHODS OF STUDYING H.EMOLYSIXS. 335 



into the subject. In passing, however, it may be mentioned that 

 for an investigation in this direction to be at all complete it is necessary 

 to make use of as many different species of blood-cells as possible. 

 The susceptibility of the cells can be extraordinarily diverse, so that- 

 certain poisons exert a marked hsemolytic effect on some species of 

 blood, while they fail to have any action whatever on other species. 

 Thus the poison of the garden spider, studied by Sachs, 1 is inert for 

 guinea-pig or dog blood-cells, while it has strong hsemolytic powers for 

 rabbit blood-cells. Crotin which dissolves certain blood-cells (e.g. 

 rabbit blood) and agglutinates others (e.g. hog blood) behaves in 

 similar fashion. 2 



In the case of the specific hsemolysins produced by immunization 

 the choice of blood, of course, is already indicated. But even here, 

 extending the investigations to numerous other species of blood 

 may lead to valuable information concerning a community of recep- 

 tors such as exists between sheep, goat, and ox 3 and as has recently 

 been shown by Marshall to exist between man and certain species of 

 monkeys. In testing a serum for the presences of isolysins it is 

 necessary to use the blood of numerous individuals, for according to 

 our experience the sensitiveness of the blood, in the case of goats, 

 is subject to the widest individual fluctuations. In this way one 

 can easily be misled to assume that the experiment results nega- 

 tively. It is advisable, when testing a fluid for hsemolytic properties 

 for the first time, to remove the serum by washing the blood-cells at 

 least once. Under certain circumstances a slight degree of hsemolytic 

 action can be masked by an antihsemolytic action of the normal serum. 

 This is seen to a high degree in the case of the haemolytic poisons 

 of the organ extracts. 4 So far as the dosage is concerned one 

 should select wide limits, especially in the first experiments. If 

 one has once determined the presence of a hsemolytic action, the 

 quantitative estimation follows by means of a more or less finely 

 graded series of experiments. Types of these experiments are found 

 on pages 168, 270, 276, etc. 



In testing a hsemolysin which has not yet been examined, it is 



1 See pages 167 et seq. 



2 Elfstrand, Uber giftige Eiweissstoffe welche Blutkorperchen verkleben. 

 Upsala, 1891. 



3 See pages 93 et seq. 



4 See Korschun and Morgenroth, pp. 267 et seq. 



