646 HISTORY OF SCIENCE. 



The discoveries mentioned in the last paragraph connect curiously 

 the animal and vegetable kingdoms. A distinction long relied upon 

 for discriminating animals from vegetables was that the food of the 

 former is organic matter, while that of the latter is inorganic. Strange 

 as it may appear to a reader unversed in modern biology, the scientific 

 demarcation of these two kingdoms of nature has proved a hard, if not 

 an impossible, task. It is, of course, only with the lowest classes of 

 each that this difficulty occurs. Not a few classes of organisms have 

 been shifted alternately from the one kingdom to the other, according 

 to the characters relied on for their distinction. An eminent naturalist 

 has proposed to provide a place for such organisms in a kind of neutral 

 territory the Regnum protisticum. 



The continuity of nature would therefore appear to be unbroken as 

 regards the two kingdoms of the organic world. Can a like continuity 

 be traced between the organic and the inorganic ? When recently the 

 developmental theory of organisms came to the front, there appeared 

 to be yet a link missing to complete the general doctrine of evolution. 

 It was that connecting the organic world with the inorganic, and an 

 old question was revived to be considered under new lights. It in- 

 volves the principle that is called '* spontaneous generation," or abio- 

 genesis, which would assert that inorganic dead matter under suitable 

 conditions is capable of evolving living organisms. Although "spon- 

 taneous generation " had been almost universally rejected by biologists y 

 there were nevertheless many instances in which organisms made their 

 appearance where the pre-existence of germs appeared to be impossible. 

 A great many experiments of this kind were detailed in a work pub- 

 lished by Dr. BASTIAN in 1871, which gave rise to much disputation. 

 Renewed investigations were made by Dr. Roberts of Manchester, 

 Professor Tyndall, and many others ; and these went to prove that 

 when certain precautions were taken to prevent the access of germs 

 floating in the air, no appearance of organism or inorganic evolutions 

 ever took place. Professor Tyndall propounded ( a theory of zymotic 

 diseases as due to specific germs in the atmosphere. All these investi- 

 gations are connected with the researches on fermentation of the emi- 

 nent French chemist PASTEUR (born 1822). There are many different 

 kinds of fermentation, and it was Pasteur's discovery that each kind of 

 fermentation is dependent upon the presence of certain organisms 

 which are different in each case. 



Geology is a science in many ways peculiar. It is one of the newest 

 of the sciences. It is continuous, by common matter and interde- 

 pendence, so to speak, with many other departments of knowledge ; 

 with astronomy, with physics, with chemistry, with zoology, with 

 botany, with mineralogy, with meteorology, with physical geography. 

 According as the study is pursued under one or the other of its relations, 

 so many branches of inquiry present themselves. The science might 

 al-so be considered descriptive, systematic, or theoretical. First, as merely 



