CHAPTER VII 



CHEMOTHERAPY AND ANTIBIOTICS 



On the whole we have been concerned until now with the processes by which 

 organisms obtain the energy and Bausteine for growth and multiplication, and the 

 changes occurring during the hfe cycle. The subject of this chapter is a brief descrip- 

 tion of the agencies by which the higher animals, especially man, can be rid of micro- 

 organisms which have found their way into parts of the body where they wreak 

 damage and destruction. Symbiosis, in which different organisms can live together 

 in harmony for the mutual benefit, has been briefly mentioned, but disease hardly at 

 all. The pathology of disease, the means by which micro-organisms damage and kill 

 their host does not concern us here, but only the methods by which the invaders may 

 be destroyed. 



The process of disinfection or killing bacteria outside the body differs in many 

 respects from chemotherapy in vivo. Not only are many potent in vitro disinfectants 

 useless in the body owing to their toxicity to the host, but when introduced into the 

 animal body chemical or even physical changes may be produced in them biologically 

 which may make them ineffective anti-bacterial agents, or in some cases more 

 effective. 



ANTIBODIES AND IMMUNITY 



In addition to this the body has its own armoury of defences which may be able 

 to deal with an infective agent when the chemotherapeutic agent holds the infection 

 in check. These defences may take the form of non-specific agencies such as the 

 white cells which can often engulf checked invaders, or specific antibodies which can 

 deal with only one closely defined type of foreign body. This plunges us into the 

 subject of immunity which cannot be dealt with, but, nevertheless, should never be 

 neglected in considerations of chemotherapy. However much we improve our 

 chemotherapeutic agents and antibiotics we can never surpass some natural anti- 

 bodies in their absolute specificity of reacting only with the one toxic agent against 

 which they have been ehcited, and being completely harmless to the cells of the body. 

 If a chemotherapeutic agent does no more it may save life if it holds invasive organisms 

 in check whilst the natural defences of the body are mobilised. Before leaving this 

 subject it should be emphasised once more that in considering the effects of chemo- 

 therapeutic agents in the body there are the following internal allies to take into 

 account : — 



(1) Non-specific rapidly mobihsed leucoc\i:es, etc. 



(2) Specific slowly formed antibodies : — 



(a) Antibacterial, acting on the bacteria themselves ; 

 (6) Antitoxic, without action on the bacteria but neutralising poisonous 

 products of the bacteria and thus protecting the host from injury. 



Even if a therapeutic agent is not bactericidal but only temporarily bacteriostatic 

 it may enable the body defences to eliminate the infection. 



Perhaps the ideal chemotherapeutic agent would have the properties of a 

 synthetic prosthetic group of an antibody ; it should be completely, rapidly and 



