HISTORICAL 9 



simple. Certain substances are placed in a bottle, the bottle is well 

 stoppered and buried in a manure heap. Every day certain incantations 

 must, be pronounced over the bottle in the manure heap. In time, Para- 

 celsus declared, a small living human being (homunculus) will appear in 

 the bottle. Paracelsus, however, naively admits that he has never suc- 

 ceeded in inducing the homunculus to continue alive after being taken from' 

 the bottle. Gradually these grotesque and extreme opinions regarding 

 tpontaneous generation were abandoned, and it was declared that only 

 she lower plants and animals, such as seaweeds, algae, lichens, lice, mites, 

 maggots, etc., could develop spontaneously. In fact, we can find fairly 

 intelligent individuals to-day who firmly believe that certain animals, as 

 lice, mites, etc., can originate without a parent, and that the hair from the 

 tail or mane of a horse will change into a worm or snake if placed in a bottle 

 of water and exposed to light and warmth. 



From the earliest records we learn that the value of disinfectants in pre- 

 venting the spread of infectious diseases (epidemics, and plagues) was 

 known. Ovid states that the shepherds of his time used burning sulphur 

 for bleaching wool and to free it from infectious diseases. In time of 

 plagues, big fires were made to stay the ravages of pestilential diseases. 

 The Mosaic law is replete with' instructions regarding cleanliness as a 

 means of preventing disease. Wine was highly valued as a dressing for 

 wounds, having the effect of preventing or checking pus formation. 



Period II 



From Leeuwenhoek (1656) to Schwann (1837). (Discovery of 

 micro-organisms and the early investigations regarding their activities.) 



As early as 1646 Kircher suggested that certain diseases might be due 

 to very minute organisms which were supposed to originate spontaneously 

 under certain conditions. Anton van Leeuwenhoek is very justly called 

 the father of microscopy, and to him must undeniably be given the credit 

 of first having discovered and actually figured microbes and other micro- 

 organisms. His Arcana Natures was published in 1656 in four volumes. 

 It is a most interesting work, and contains many good illustrations showing 

 microbes of the mouth cavity, infusoria of stagnant water and cellular 

 structure of vegetable tissues. He observed the motion of bacteria and in- 

 fusoria, made measurements, illustrated capillary circulation in the web 

 of the frog's foot, etc. He was closely followed by Robert Hooke, who 

 published his Micrographia in 1658. The discoveries of Leeuwenhoek 

 and Hooke were certainly epoch-making. A new world of minute organ- 

 isms was made known, the question of spontaneous generation received a 

 new turn, and the way to the discovery of the causes of disease and fer- 



