SCIENTIFIC PROGRESS. 491 



process of fecundation and generation, which theretofore had been 

 wrapped in the deepest obscurity. Four years later, in 1848, fol- 

 lowed Du Bois-Reyniond's researches in animal electricity and the 

 proof that the nerve is not, as formerly believed, a mere conductor, 

 but a self-generator of the electricity originated by chemical me- 

 tabolism and the transformation of what is designated as potential 

 force or elasticity into living force or motion by virtue of the great 

 principle of the conservation of force. 



Under the head of physiology, special mention must also be 

 made of the great successes that accompanied the researches of 

 Messrs. Schiff, Ferrier, Munk, Nothnagel, Hitzig, Fritsch, Broca, 

 Flechsig, and others concerning the localization of the various 

 activities of the soul, or the divisions of labor taking place in the 

 brain, and the topographical distribution of certain functions of the 

 brain on its surface — researches which have not by any means 

 reached their end. The most important among these is the discov- 

 ery, made first by Broca, in 1861, of the controlling center of speech 

 at a definite place in the fore part of the brain. Morbid degenera- 

 tion or destruction of this spot is the cause of aphasia, or speechless- 

 ness. This discovery also satisfactorily explains why the large man- 

 like apes which are almost devoid of that part of the brain can 

 not speak, notwithstanding the formation of their larynges is similar 

 to that of man. Not less important are the entirely new researches 

 of Professor Flechsig on the so-called centers of association in the 

 brain and the definite proof furnished by him that all thinking 

 springs from the senses, inasmuch as it is only by the gradual devel- 

 opment of those centers that the action of the different organs is con- 

 nected, and thus thinking and intelligence are made possible. 



Zoology. — Besides the numerous acquisitions of systematic zo- 

 ology, special mention should be made here of the researches as to 

 the life in the sea. These have been prosecuted largely through 

 the zoological marine stations supported by Government, and have 

 been rendered more effective by means of improved apparatus which 

 made possible the acquisition of knowledge as to the deep-sea fauna. 

 The results enabled Haeckel to establish his renowned Gastrsea the- 

 ory, according to which all animal species — however far differenti- 

 ated — owe their primal origin to a single primitive form of the great- 

 est simplicity that might be properly designated as " primitive stom- 

 ach." To the zoological researches of the century we are also 

 indebted for the better knowledge of those strange animal creatures 

 nearest to man whose existence was still doubted or relegated to the 

 realm of fable as late as the last century even by scholars, although 

 as early as 500 b. c. the Carthaginian Hanno had seen gorillas on the 

 western coast of Africa, and described them as wild " haired men." 



