88 JOURNAL OF THE [April, 



This law is coeval with the existence of life. To ascertain and 

 understand the conditions favorable to the human race has and 

 will always occupy the attention of a large portion of the more 

 intelligent of mankind. 



Some of the conditions are at once apparent; others, equally 

 important, are unseen, obscure, and only discovered by tracing 

 back from the effect to the cause. We experience effects and not 

 causes, and to analyze the former, assigning each to its proper 

 cause, is by no means an easy matter. The first step is to observe 

 the facts, study their relations, and trace the laws controlling them. 

 It is only in this way that any progress has been made, and then 

 oftentimes the real nature of the cause remains undiscovered. 



Jenner's important discovery of vaccination for small-pox, a 

 century since, was not the result of accident, as often stated, but 

 close observation of a series of facts and studying their relations. 

 That small-pox was due to a germ in the system, invisible to the 

 keenest vision, is of recent demonstration by the microscope. 



How early minute forms of life were suspected of causing bod- 

 ily ailments or decomposition in fluids is uncertain. The Egyp- 

 tians, 3,500 years since, knew how to practically prevent deconi- 

 position in bodies and wooden utensils, so that they have been 

 preserved to the present time. More recently Robert Boyle, 

 200 years ago, expressed the opinion that ferments had something 

 to do with fevers. Leuwenhoek, 1632 to 1723, made small lenses, 

 and described the ferment of yeast as ovoid or spherical bodies, 

 and discovered bacteria in the mouth and in fluids undergoing 

 decomposition. The powers and use of the early simple micro- 

 scopes were too limited to definitely establish the functions of the 

 minute forms or their relations to the higher orders The belief, 

 however, was becoming more and more general that the minute 

 forms had something to do with bodily ailments and fermen- 

 tations, but without microscopical aid it could not be clearly 

 demonstrated. As must be expected, some extravagant views 

 were adopted, while others were close approximations to the truth. 

 Boerhaave, in 1693, distinguished three kinds of fermentations, 

 viz , alcoholic, acetous, and putrefactive. Linnaeus stated that 

 a certain number of diseases resulted from animated invisible 

 particles dispersed through the air. Spallanzani, in 1769, started 

 his series of experiments upon spontaneous generation and ste- 



