386 THE HISTORY OF BIOLOGY 



the finality of mathematical conclusions, however useful they may have been 

 to science. Miiller's ideas, however, deserve all possible attention; there is 

 no doubt that he largely created the standard of thought which prevailed in 

 biological circles up to the appearance of the origin-of-species theory, and 

 from which the opposition to that theory largely recruited its forces. At any 

 rate, this legacy of Miiller's from the age of romantic natural philosophy 

 certainly had its influence on successive generations; it even crept into bio- 

 logical theories fairly effectively, although in a roundabout way, during 

 the greatest days of Darwinism. 



The influence of Miiller's physiological text-book has been all the greater 

 because its special section contains information of great value based on the 

 results of his own original research-work; here we find a very careful and 

 exhaustive account of the law of specific mental energies to which we have 

 previously referred, and here are explained in a manner unexcelled by his 

 age the functions of the nervous system; here his above-mentioned investiga- 

 tions on that subject are summarily described. Further he declares that the 

 ganglion-cells of the brain perform the latter's functions, and he explains 

 the connexion between them. Specially noteworthy in this respect as a 

 summary of his results is the chapter on "Mechanik des Nervetiprinzips," 

 wherein his keen powers of observation and combination, undisturbed by 

 any philosophical adjuncts, are very conspicuous. His exposition of the 

 alimental and vascular systems, as well as of the sexual organs, is very fine, 

 although somewhat brief. 



After the "text-book" had been completed, Miiller gave up physiology. 

 According to his own statement, he shared Rudolphi's dislike of experi- 

 menting on live animals, as practised by Magendie and his school, and his 

 physiological works were actually based very largely on comparative ana- 

 tomical observations. He clearly realized that physiology could not be carried 

 any further in this way and he consequently went over entirely to compara- 

 tive anatomy, which at that time had very large fields of inquiry still un- 

 exploited. Miiller made a particularly happy choice when he devoted himself 

 to investigations into the structure of the lowest Vertebrata. Among his 

 works on this subject may be mentioned his monograph on the lancet-fish, 

 which exhaustively supplements Rathke's previously mentioned work on 

 that animal. But in connexion with this group special mention should be 

 made of his monumental work on the skeleton-system, muscles, and nerves 

 of the Myxinoidei, on which he spent nearly ten years. He took up for study 

 this subject of the most primitive group in the order of Cyclostomi because, 

 as he says, the boundary forms in a class are the most interesting in that they 

 lose a good deal of the character of the class and thereby show us the type 

 of the class in its most simple form. The work contains a detailed description, 

 exemplary in its accuracy, of the said organic systems in the Myxine glutinosa 



