BOTANY AND MEDICINE 447 



molds and soil bacteria began in our generation, it must be noted that molds 

 were employed for similar purposes by the Chinese thousands of years ago. 

 And several hundred years ago North American Indians are known to have 

 employed both soil and rotting wood for the prevention of wound infections 

 and for healing festered cuts. Nevertheless, the penicillin discovery was the 

 forerunner of the modern antibiotic age, and it undoubtedly set the stage 

 for a tremendous interest in the re-investigation of lower and higher plants 

 for new biologically active constituents. More than a thousand plant species 

 have now been screened for newer antibiotics, and at least two hundred anti- 

 biotics have been discovered in living organisms since 1929. Yet, thus far 

 only about a dozen therapeutically useful antibiotic compounds have been 

 successfully isolated from molds, bacteria, and soil actinomycetes, all lower 

 plants. Most of these have been procured since 1939 when Dubos isolated 

 tyrothricin from the filtrates of cultures of Bacillus brcvis; streptomycin was 

 discovered from cultures of an actinomycete in 1944, bacitracin in 1945, 

 polymyxin and Chloromycetin in 1947, aureomycin in 1948, terramycin in 

 1950, and erythromycin in 1952. 



More than one hundred higher plants have also been studied for thera- 

 peutically effective antibiotics, and although antibacterial compounds have 

 been procured, their usefulness in therapy has not been significant either 

 because of toxicity or their ineffectiveness when employed clinically. These 

 sources have included such plants as garlic {Allium spp.), the wild ginger 

 {Asarum spp.), senna leaves {Cassia spp.), honeysuckle, blessed thistle, and 

 lichens such as Spanish moss {Ramalina spp.), and Rocella. Several other 

 higher plants might be included with the list. 



The well-established and the less well known antibacterial compounds 

 which we possess do not thoroughly meet the requisites for the most ideal 

 antibiotic, and the search must therefore continue. Since some bacteria possess 

 abilities to become antibiotic-resistant and since there are large numbers of 

 pathogens which remain outside the sphere of antibiotic influence, man is far 

 from secure in his reliance upon the chemotherapeutic agents of this type. 

 Furthermore, although total penicillin and chloramphenicol synthesis have 

 been accomplished, unfortunately the production of them via the test tube 

 is beset with numerous problems which have delayed the economic applica- 

 tion of such synthesis methods. Tetracycline (Achromycin) is, of course, 

 obtained by a semi-synthetic process from the naturally occurring antibiotic 

 chlortetracycline. It is thus reasonable to expect that the parade of new 

 agents in this field from living organisms will continue and perhaps increase 

 at as rapid a rate as it has since 1944. 



Vasodilators and antihypertensive agents. Since glyceryl trinitrate was 

 discovered by Sobrero in 1847 and amyl nitrite was introduced to medical 

 practice by Guthrie about ten years later for the treatment of angina pectoris, 

 nitrites and organic nitrates have been, with few exceptions, the outstanding 



