170 COLLECTED STUDIES IN IMMUNITY. 



tive results; the sera of man, rabbit, horse, pig, dog, rat, guinea- 

 pig, goat, sheep, ox, goose, and pigeon, inactivated by heating to 

 56 C. in order to eliminate any possible solvent action, were unable 

 even in amounts of 1.0 cc. to protect rabbit blood against just a com- 

 plete solvent dose of arachnolysin. 



On the other hand, the study of the poison's behavior toward 

 sensitive and insensitive cells has yielded results of special interest 

 in connection with the receptor theory. Certain species of blood, 

 such as dog or guinea-pig blood, have shown themselves immune 

 to the spider poison. This presents the most favorable conditions 

 for studying the relations between the binding of poisons and their 

 action. This point, as we have seen, is of the greatest importance 

 for the view that serum haemolysins are toxin-like bodies. 



If arachnolysin is a blood-poison whose action is due to the anchor- 

 ing of a certain haptophone group to a receptor of the sensitive blood- 

 cell, and if, corresponding to this, the immunity of certain species 

 of blood is due to a lack of appropriate receptors, it follows that 

 the sensitive blood-cells must be able to bind the active principle 

 of such a poison solution, while the insensitive cells leave it entirely 

 unaffected. 



So far as the insensitive bloods are concerned, the method of 

 making the experiment is very simple. Dog blood is mixed with a 

 certain quantity of arachnolysin, kept in the incubator for an hour 

 and frequently shaken. Thereupon the blood, which, of course, is 

 unchanged, is separated by means of a centrifuge. The decanted 

 fluid, compared with the original material, shows not the least diminu- 

 tion of its solvent power on rabbit blood-cells. This shows that the 

 insensitive dog blood is not able to bind the arachnolysin. 



In the case of the sensitive blood-cells, the demonstration of the 

 combining power is much more difficult, for these, when tested in 

 a similar manner are dissolved, so that it is impossible to separate 

 blood-cells and fluid. We can then only operate with the laky blood 

 solution, the inactivity of which permits of no direct conclusion 

 that a binding of the poison by means of receptors had occurred. 

 Furthermore, if the poison solution has lost its power as a result 

 of the action already exerted, there is no means by which this can 

 be determined. It was necessary, therefore, to employ blood-cell 

 material which had been made stable so far as the vital influences 

 of the haemolysis were concerned, without, however, losing its chemi- 

 cal character. For this purpose we used blood-cell stromata, by 



