2IO 



NATURE 



[November 6, 19 19 



PREVENTIVE MEDICINE SINCE 1869. 



By Dr. C. J. Martin, F.R.S. 



PREVENTIVE medicine is concerned with the 

 application of knowledge to the prevention 

 of disease. To this end all the sciences have been 

 laid under tribute, but physiology, pathology, 

 bacteriology, and epidemiology to the greatest 

 extent, as these have the more immediate bearing. 



The rapid progress of preventive medicine 

 during the last half-century is due primarily to 

 the increase of physiological and pathological 

 knowledge, and pre-eminently to the completer 

 understanding of the process of infection which 

 has been acquired during this period. So long as 

 defective development and disease were regarded 

 as wholly constitutional or inherent in the in- 

 dividual, the only prospect of improvement lay 

 in the weeding out of the unfit by the ruthless 

 process of natural selection. A greater hopeful- 

 ness has, however, arisen as the part played by 

 prejudicial environmental conditions, such as im- 

 proper feeding and housing, undue fatigue, the 

 abuse of alcohol, and, above all, the invasion of 

 pathogenic agents, was realised. 



By the end of the 'sixties the necessity of sup- 

 posing a contaghim vivuin as the cause of 

 many diseases was fairly generally recognised. 

 Pasteur's researches on fermentation and putre- 

 faction had led him to the opinion that infectious 

 diseases might be interpreted as the result of 

 particular fermentations due to specific microbes, 

 and it was the ambition of his life to substantiate 

 this conception. Lister had launched his anti- 

 septic methods on the basis of Pasteur's work, 

 and these were already beginning to revolutionise 

 surgical practice. Villemin had just demonstrated 

 that tuberculous diseases, hitherto regarded as 

 "constitutional," were due to a common infective 

 agent capable of multiplymg indefinitely in the 

 bodies of animals and of being handed on from 

 one animal to another by inoculation. Hitherto, 

 however, although various microscopic organisms 

 had been found to be associated with disease, and 

 indications had been obtained of their aetiological 

 significance, not one of them had been isolated. 

 The causal relationships claimed were thus un- 

 proven and much of their life-history unknown. 



The first isolation and propagation in pure 

 culture of a pathogenic organism took place in 

 1876, and was accomplished by Koch in the case 

 of a bacillus derived from cases of splenic fever 

 or anthrax. Inoculations of cultures made in 

 vitro into animals reproduced the disease. Pro- 

 gress in bacteriological discovery remained slow 

 until in 1880 more appropriate methods for the 

 isolation of bacteria were derived by Koch. 

 Then followed a period of extraordinary fertility. 

 Within fifteen years the causal agents of cholera, 

 typhoid fever, diphtheria, tuberculosis, various 

 types of suppurative processes, gas gangrene and 

 erysipelas, glanders, gonorrhoea, pneumonia, 

 food poisoning, meningitis, Malta fever, leprosy, 

 NO. 2610, VOL. 104] 



I and plague, as well as of a larger number of 

 diseases of animals, were discovered. 



The discovery of pathogenic agents of another 

 I kind soon followed. The association of relapsing- 

 I fever with the presence of a minute motile spiral 

 I organism in the blood was observed by Ober- 

 meier in 1873. Later, a number of diseases 

 of man and animals were found to be caused by 

 various spirochaetes, most important among them 

 being relapsing fevers, syphilis, yaws, and infec- 

 tive jaundice. 



In 1881 Laveran described the parasite of 

 quartan malaria. This observation was followed 

 by the discovery of more than a hundred micro- 

 parasites belonging to the protozoa which are 

 responsible for diseases in higher animals. The 

 most important human diseases due to protozoan 

 parasites are the three types of malaria, sleeping 

 sickness, and kala azar. 



Another class ,of pathogenic agents which is 

 already known to be responsible for upwards 

 of thirty separate diseases of man and animals 

 remains to be mentioned. These viruses are 

 either on the margin of visibility or invisible with 

 the microscope. They are so small as to pass 

 through biscuit porcelain. The causal agents of 

 infantile paralysis, yellow fever, niolluscum con- 

 tagiostim, dengue fever, the three-day fever of the 

 Mediterranean, and typhus fever belong to this 

 category, as well as those of many important 

 animal diseases, as rinderpest, horse sickness, and 

 foot-and-mouth disease, and there are a number of 

 indications that the infective agents of the common 

 exanthemata — measles, scarlet fever, smallpox — 

 are at some period of their life-history so small 

 as to be included amongst the "filter-passers."' 



Since 1880 the setiological fa'fctor of most human 

 maladies has been brought to light. A correct aetio- 

 logy is fundamentally necessary, bu": for preventive 

 measures mere identification of the cause of a 

 disease is not sufficient. The life-history of the 

 parasite within and without its host, and particu- 

 larly the channels and method of entrance and 

 exit, must be known if a successful attack is to 

 be made upon it. Indeed, some of the most 

 striking triumphs of preventive medicine have 

 been gained in the case of diseases in which the 

 virus had not been seen or isolated (such as 

 hydrophobia, yellow fever, and trench fever), but 

 in which, nevertheless, many properties of the 

 virus and the method w-hereby it effected entrance 

 and exit had been revealed by experiment. 



In the first half of the period under review 

 researches were more particularly directed to the 

 discovery and isolation of the causative factors of 

 disease ; the latter half, for the reasons outlined 

 above, has been characterised by the amount of 

 knowledge gained regarding the details of the 

 life-history of various parasitic agencies, the 

 maintenance of the infection in the absence of 



