PRINCIPLES OF CHEMOTHERAPY 785 



diseases in which the specific microorganism was known and could be 

 cultivated. 



In the foregoing chapters we have reviewed our knowledge of the 

 nature of these specific remedies produced by the body-cells and called 

 antibodies. In Chapter XXX we have also reviewed the application of 

 these remedies in the treatment of various infections, and have pointed 

 out their limitations and the difficulties encountered in their production. 

 Naturally, in the early days it was deemed necessary and advisable to 

 utilize a lower animal for the manufacture of these antibodies. With 

 the discovery of a means of attenuating or modifying a disease-producing 

 parasite it was found possible to inject these vaccines into our own 

 bodies, and thus stimulate our own cells to produce the specific anti- 

 body a method that had been introduced empirically years before by 

 Jenner in vaccination against smallpox. 



As was previously stated, scientists have long believed that it was 

 possible to find or produce chemical substances that would not unite 

 with the blood albumin or body-cells, but would have a highly selective 

 and germicidal action on microparasites and prove capable of killing 

 these in the living body. Curiously enough Ehrlich, to whom we are al- 

 ready indebted for much of our knowledge of the intricate problems 

 of cell life, and especially the mechanism of their defense and offense 

 against parasitic invaders, has again taken the lead and set about testing 

 hundreds of compounds in a painstaking, logical, and scientific manner, 

 in the hope of finding one that would prove most germicidal for various 

 trypanosomes and spirochetes, and at the same time be least toxic for 

 the body-cells. These researches finally culminated in the discovery 

 of the arsenical compound now popularly known as salvarsan. This 

 discovery constitutes a great triumph for medical science, not only be- 

 cause of the intrinsic value of the drug in the treatment and cure of 

 syphilis and frambesia, but because it demonstrates the truth of a prin- 

 ciple, and has opened up vast possibilities for future investigation. 



PRINCIPLES OF CHEMOTHERAPY 



Organotropism and Parasitotropism. The guiding principle in 

 chemotherapy is to imitate nature's method of overcoming an infection 

 by the aid of substances that destroy the microorganisms, while the 

 body-cells of the host are left unharmed. To this end the chemical 

 agent employed must possess a much stronger affinity for the micro- 

 organisms than for the body-cells to quote Ehrlich, it must be more 

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