422 PROGRESSION OP 



which, no doubt, perform the same functions as far as required in 

 those animals, and are, in fact, some at least, brains also to them, 

 but of a different form and accommodated to their structured In the 

 same way the heart is not one mass in the cuttle-fish but three, and in 

 the lowest none exists, vessels carrying on the circulation. It was, 

 not many years ago, customary to assert that many animals have 

 no nervous system. " It was reserved for the modern spirit of ob- 

 servation," says Professor Tiedemann, "to establish the presence of 

 nerves in many of the most inferior animals the star-fish, actinia, 

 pyrosoma, ascidia, and some entozoa, in which their existence was 

 denied in Haller's time."y Professor Ehrenberg has lately shown 

 that the infusory animalcules possess nerves and even ganglia, as 

 well as eyes, muscles, and sexual and digestive organs, and pro- 

 bably vessels, though myriads can exist in a dot : the verticella 

 rotatoria being only from yj^ to J ^ of an inch in dimension. 2 In 

 regard to brutes in which nerves are not yet found, Dr. Tiede- 

 mann allows that, " as we perceive in these animals phenomena 

 which take place by the medium of nerves in animals of a more 

 elevated order that is to say, sensibility and voluntary motion 

 it is not improbable that, in them, the nervous substance is 

 mixed with the gelatinous or mucous mass, without being demon- 

 strable as a particular tissue." 



The higher we ascend, the more parts exist above the chorda 

 oblongata, till, rising from fish and reptiles, through the numerous 

 warm-blooded brutes, all distinguished by the relative magnitude 

 of each cerebral part, according to their several mental characters, 

 and seeing the successive additions of cerebral structure and 

 cerebral mass, and of intelligence, we arrive at man, in whom the 

 successive impositions of cerebral matter has reached its maximum, 

 so that the summit of the nervous system, which corresponds 

 with the forehead and vertex, is much larger in him than in any 

 brute a , and his intellect and moral feelings are proportionally 



x Gall, 1. c. 8vo. t. i. p. 25. sqq. 



y Systematic Treatise on Comparative Physiology, by F. Tiedemann, M. D. Prof, 

 of Anat. and Phys. in the Univer. of Heidelberg, translated by G. J. M. Gully, 

 M.D., and J. H. Lane, M.D. 1834, p. 64. See my remarks, suprti e , p. 4. 



z See accounts of Prof. Ehrenberg's discoveries by Dr. Gairdner, and my 

 colleague Prof. Sharpey, in the Edin. New Philos. Journal, 1831, 1833. 



a See Gall, 1. c. 4to. vol. ii. p. 252. 364. sqq. ; 8vo. t. ii. p. 153. sqq. 365. 

 sqq., t. vi. p. 298. sqq. 



