2S4 Professor Mi'iller on the Life and Writings of 



other explanations. For a long time he carried on experiments on 

 incubation ; the results were not exactly in favour of the idea of 

 the gill-arches ; but still there was much observed in the course 

 of these experiments, which shewed a far greater resemblance 

 of the state of the foetus in birds to that of fishes than miffht 

 have been anticipated. The idea that man during his develop- 

 ment, passed through the other degrees of animal life, was quite 

 in opposition to his views, and in that he was quite right. The 

 existence of gill-arches in the neck of embryos, would not, 

 however, have disturbed Rudolphi, had he not perhaps also 

 rejected the idea of unity of organization in the different classes 

 of vertebrate animals, along with the idea of the passing through 

 the various grades of animals. How he explained these undoubt- 

 edly existing arches and slits in the neck of embryos, has never 

 been very clear to me. He probably already adopted the pro- 

 per opinion, that the general plan for all vertebrate animals is 

 at first similar ; that, however, it is only in fishes that gills are 

 formed on those arches, while in other animals these arches 

 partly gradually disappear, and partly become changed into 

 the horns of the os hyoides. In his doubts respecting opinions 

 ■which were adopted by others, but not by himself, Rudolphi 

 was neither reserved nor obstinate : good arguments always pre- 

 vailed with him, and he willingly gave up his opinion when con- 

 vinced of its want of foundation. He had not seen the connec- 

 tion of the vesicula umhilicaUs with the intestinal canal by 

 means of a passage, probably because he examined old eggs; still 

 in 1828 he was prejudiced against it. Professor Gurlt shewed 

 him the connection of a diverticiihim ilei with the navel, and 

 he became doubtful respecting the explanation he had given. 



Rudolphi's tendency in physiology was the criticism of ob- 

 servations and of prevailing doctrines. The time at which he 

 began his labours was a brilliant one for physiology. After 

 the discovery of galvanism, by Aloysius Galvani, that phe- 

 nomenon was for a long time regarded by the first natural 

 philosophers and physiologists as a physiological one. When 

 this view was afterwards disproved there was still an opportu- 

 nity of discovering the laws of animal irritability, and on this 

 path, which was opened by A. von Humboldt, many natural 

 philosophers and physiologists followed. Rudolphi so far took 



