434 HUMAN BIOLOGY 



functional neuroses and early mental disorder can thus be 

 elucidated; mental hygiene is a branch of the preventive 

 medicine which is essential in connection with the neuro- 

 logical and psychiatric out-patient clinics of a hospital. 



The immediate or directly responsible causes of disease 

 include the numerous infections, the various forms of 

 mechanical injury, and negative factors such as the absence 

 of an internal secretion or of a vitamin essential to the 

 maintenance of health. The knowledge of the immediate 

 exciting causes of the infectious diseases is due to the 

 sciences of bacteriology and later of protozoology, and is one 

 of the greatest milestones in the history of medicine. In 

 the sixteenth century Hieronymus Fracastorius of Verona 

 spoke of the "seeds" of contagion passing from one person to 

 another, and was the first to compare infection with vinous 

 fermentation; but the real founder of bacteriology was 

 Louis Pasteur (1822- 1895) a chemist and not a medical 

 man, and with his the name of Robert Koch (1843-1910) of 

 Berlin will always be associated as a pioneer in its advance 

 and in the methods of specific treatment for diseases due to a 

 known microbe. The epoch-making discoveries of the 

 microorganisms responsible for diphtheria, tetanus and 

 typhoid fever, and so of measures for their prevention and, 

 to take a more modern instance, the successful elaboration 

 of insulin in the treatment of diabetes mellitus, would 

 have been impossible without animal experiments. Yet 

 many well-meaning but ill-advised people, unmindful of 

 our Lord's words "Ye are of more value than many spar- 

 rows," have bitterly opposed the practice of vivisection; it is 

 perhaps best, and certainly most charitable, to assume that 

 they know not what they do, and will not realize the truth 

 until it is revealed to them by seeing their young child 

 gasping for breath and dying for want of antidiphtheritic 

 serum. Pasteur did not see the virus of canine rabies or 

 human hydrophobia, but following in the footsteps of 

 Edward Jenner (1749- 1823), who in 1798 made public the 

 vaccination with the material of cowpox (vaccinia) as a 

 protection against human smallpox, he gave an emulsion or 

 vaccine of the virus of rabies, at first weakened or attenuated 

 and then gradually intensified, to persons bitten by mad dogs 



