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can only act in the body when chemically bound to the cellular 

 protoplasma. On this axiom was founded the side-chain theory. 



So if a stuff is to be found that kills the parasites in the 

 body of their host, it must have affinity tho the cellular proto- 

 plasma of the parasites and not to that of the host, it must 

 be parasitotrope and not or less organotrope. 



This is the case with many curative sera that act only at 

 the corresponding bacteria and as Ehrlich expresses himself, 

 like a kind of magical bullets hit always and only their aim 

 and nothing else. 



So of all curative methods the serum method is by far the best 

 one, but in many cases of infection, especially with higher orga- 

 nised parasites, a strong and durable immunity is not to be got. 



It is therefore necessary to look for chemical agents to kill 

 those parasites, but then always arises the difficulty that the 

 remedy less or more affects the protoplasma of the infected 

 body itself. 



To make the medicament less organotrope and more para- 

 sitotrope by changing its chemical constitution, is the task that 

 comes next and was succesfully fullfîlled with the organic arsenic 

 compounds, turning out at last the wellknown salvarsan. 



To decide in trypanosomiases whether a certain remedy cures 

 ore not. experiments with living animals are indispensable and 

 of course can be made in different ways. 



Ehrlich advised to try a cure of the first attack of the 

 disease, with a dose as large as possible. This is the therapia 

 sterilisans magna. The following attacks are much more difficult 

 to deal with, than the first one, a fact we know to be the 

 same with the treatment of tertian malarial fever, where big 

 doses of quinine often bring about a real cure in the beginning 

 while a less intensive treatment leads to relapses that are 

 influenced by quinine treatment but not easely thouroughly cured. 



There are two reasons for this, first the production of new 

 forms of the parasite, the gametes, second that the parasites 

 themselves acquiesce a power of resistance against the drug, 

 just like the human body can get accustomed to a certain 

 extent against arsenic or alkaloid poisoning. 



In such cases an other remedy must be used and so during 

 my station at Balik Papan (Borneo) I sometimes succeeded in 



