"Quite so," said Lionel. "You're a serumite, I'm not. I am not at all keen on the use of serum for this complaint. I believe that the cure (if there is one) will be got by injecting the patient with dead trypanosomes or very, very weak ones. I'm going to make a special artificial culture of trypanosomes in culture tubes. I shall then weaken the germs with atoxyl. When they are all bloated and paralysed, I shall inject them. I believe that that injection, or the injection of quite dead trypanosomes, will have permanent good effects."
"And I," rejoined Roger, "believe that your methods will be useless. I believe that the cure (if there be a cure) will be obtained by the use of sera obtained from naturally or artificially immunised animals."
"That's just the taking kind of fairy story you would believe. You're a sentimentalist."
"Very well. But listen. It is said that when the dogs of the bushmen are reared entirely on the meat of immune game, they become immune like the game; but that if they are not used to wild meat they develop nagana from eating it casually."
"I don't believe the first part of that," said Lionel. "It sounds too like a yarn. The dogs which are reared entirely on wild game are probably naturally immune native dogs, bred originally from some wild strain, like the wild hunting-dogs."
"But there is no doubt that wild game, like wildebeests, koodoos, hyenas, and quaggas, are immune?"
"None whatever."
"Then could not some preparation be made from the blood of the wild game? Surely one could extract the immunising principle from the immune creature, and use that as a serum?"
"We don't even know what the 'immunising principle' may be; so how can we extract it?"
"Well, then. Use the blood serum by itself."