84 Messrs. J. A. Gunn and R. St. A. Heathcote. 



animal become more resistant to the toxin. Eelatively few observations 

 seem to have been made on this point, though it might afford an explanation 

 of many problems, for example, why a high degree of immunity may exist 

 with the presence of a feeble antitoxin in the blood, and why immunity 

 should in some cases persist after antitoxin has disappeared from the blood. 

 There can be no doubt that this is a question of fundamental importance 

 which demands a larger share of attention than has so far been bestowed 

 upon it. 



Camus and G-ley (10) found that the washed red corpuscles of a rabbit- 

 immunised to eel serum showed augmented resistance to the hsemolytic action 

 of this serum. No quantitative determinations are given but it is stated that 

 the increased resistance was sometimes very slight. 



Kossel (11) stated that the red cells of rabbits immunised to eel serum, 

 and carefully freed from serum, became more resistant to the haemolytic action 

 and in proportion to the grade of immunity ; but he gives no details of the 

 experiments. 



Later Camus and Gley (12) found no increased resistance of the red cells in 

 rabbits after prolonged immunisation to eel serum, but in an animal rapidly 

 immunised (by four injections in six days) they found that some of the 

 corpuscles were not haemolysed even by high concentrations — an effect due, 

 they suppose, to the fact that the less resistant corpuscles have been 

 destroyed. 



On the other hand, Cushny (13) found that the blood of a rabbit immunised 

 to 5000 times the minimum lethal dose of ricin still showed agglutination 

 like that of a normal rabbit, only it appeared " even somewhat more sensitive." 

 Jacoby (14) who immunised a goat for eleven months and at intervals tested 

 the resistance of the red cells, found them still agglutinable, when free from 

 serum, even in the highest stages of immunity. He pointed out that the 

 possibility of cellular immunity of the red cells occurring in still higher stages 

 of immunity was not excluded. 



Calmette (15) stated clearly, though so far as I can find he did not 

 subsequently publish details of his experiments, that the red blood corpuscles 

 of an animal, immunised to cobra venom and which yielded a very antitoxic 

 and antihaemolytic serum, were still perfectly hsemolysable after being freed 

 from serum, by feeble doses of venom to which had been added a little normal 

 serum heated to 62°. 



So far as concerns the red blood corpuscles, therefore, no acquired cellular 

 immunity has been found except to eel serum ; and apparently with ricia and 

 cobra venom observers have hesitated to commit themselves to the paradoxical 

 result that the red cells may become actually more sensitive. 



