CILIA. 



625 





oscillatory motion was communicated by the 

 agitation of the globules underneath it. He 

 perceived the motion in question in no part 

 but the labial appendages, and he imagined it 

 to be connected with the male generative func- 

 tion, of which he therefore conceived the parts 

 mentioned to be the organs. It is obvious that 

 the appearance seen by Ehrman was the undu- 

 lating motion of the cilia, which organs, how- 

 ever, he had not recognised. He makes no 

 mention of currents, and consequently could 

 not perceive the connexion of the phenomenon 

 with respiration, which was also less likely to 

 occur to him, as he supposed the motion to be 

 confined to the appendages mentioned. 



The observations of Ehrman led Treviranus 

 to investigate the subject;* and he distin- 

 guished two different motions, the one a mus- 

 cular contraction, the other the peculiar motion 

 alluded toby Ehrman. The latter motion had 

 the appearance of a trembling or flickering 

 of innumerable points, and seemed at some 

 places as if produced by a moving fluid, and 

 at others by the agitation of oblong vibrating 

 organs. It was peculiarly distinct alongside 

 each of the bars of the gills and appendages. 

 He farther perceived that the agitation on the 

 surface of these parts caused an eddying mo- 

 tion in the water in which they lay, and also 

 set in motion globules of blood which had 

 escaped from the vessels. On breaking down 

 the parts into small fragments, he found that 

 each retained its power of motion, by which 

 they moved in most manifold directions, the 

 larger masses at the same time contracting and 

 dilating themselves. From these observations 

 Treviranus concludes that the bivalve Mollusca 

 afford an example of a structure in which the 

 integrant parts possess an independent vitality. 

 Their independent vitality shews itself in the 

 persistence of their automatic motion after 

 solution of organic connexion with each other, 

 and this motion is intermediate in its nature 

 between the spontaneous movements of organic 

 molecules in infusions, the male semen, &c. 

 and the motion of muscular parts, which re- 

 quires the integrity of the texture and the 

 application of a stimulus. These reflections 

 on the relation of the phenomenon to the 

 general laws of organization are the sole infe- 

 rences which he draws from his observations. 

 He notices the motion of the water only as a 

 concomitant and subordinate circumstance, not 

 having been aware of its determinate direction, 

 its relation to the respiratory process, or, in 

 short, of its being the chief end and effect of 

 the motion of the cilia. 



The next researches on the subject are those 

 of Huschke, narrated in a paper in the Isis for 

 1826.f Not having seen the original, we must 

 content ourselves with a brief notice of them to 

 be found in Burdach's Physiologie.J It is there 

 stated that on detaching a portion of the gill 

 of the Fresh-water Mussel (Unio pictorum), 

 Huschke found that the water " moved up- 



* Vermischte Schriftcn, Band iii. p. 234. 



t P. 623. 



j Band iv. p. 434. 



wards en one side, and then in an eddying 

 manner back again." 



Raspail, in a memoir on a species of fresh- 

 water polype, published in 1828,* pointed out 

 the analogy between the phenomena exhibited 

 by the gills of Mollusca and those observed in 

 infusory animalcules and polypi. 



Ciliary currents were now described by vari- 

 ous other writers of eminence, but their causes 

 were very commonly mistaken: among the 

 number may be quoted Poli,f Delle Chiaje,J 

 Carus, De Blainville,|| and Unger.^f 



Having observed currents produced in other 

 instances by an impelling power inherent in 

 the surfaces over which the fluid passed, I was 

 myself led to suspect that the respiratory cur- 

 rent in bivalve Mollusca was of the same kind, 

 or that it was caused by an impulsion commu- 

 nicated to the water by the surface of the gills 

 and other parts over which it was conveyed in 

 its passage, without being aware of any similar 

 view having been entertained by others. I 

 then observed the determinate direction of the 

 impulsion along the surface, together with the 

 arrangement and action of the cilia. These 

 observations were published at the time (1830) 

 in a paper already mentioned,** in which also 

 the respiratory currents of the bivalve Mollusca 

 are considered as a particular exam'ple of a 

 more generally prevailing phenomenon. 



In a paper on the circulation of the blood, 

 in Magendie's Journal for 1831,ft there are 

 some remarks pertaining to the present subject, 

 from which it appears that the author, M. 

 Guillot, had observed the ciliary motion of the 

 gills of the Sea-mussel and Oyster. He has, 

 however, like Baker, mistaken the regular un- 

 dulations of the cilia for the circulation of a 

 fluid within vessels. He takes no notice of 

 any motion or current excited in the water. 



Carus,|J in a memoir on the development of 

 the River-mussel, states that he observed an 

 undulatory or oscillatory motion of the gills, 

 and that by this motion, which he conceives to 

 be in the substance of the gill, the water is 

 propelled, and the general respiratory current 

 through the branchial cavity produced. It is 

 obvious that what he calls an oscillation of the 

 substance of the gill, and which he erroneously 

 supposes has previously escaped attention, is 

 merely the undulatory motion of the cilia. 



The last researches on this subject which we 

 have to notice are those of Purkinje and Va- 

 lentin^ As above stated, they discovered the 

 ciliary motion in the alimentary canal of the 

 Mollusca, having found it in the Lymnsca, Pa- 

 ludina, and the Fresh-water mussel. 



* Memoires de la Soc. d'Hist. Nat. de Paris, 

 tome iv. p. 131, seq. Chimie Organique, 1833, 

 p. 246. 



t Testacea utriusque Siciliae, t. i. 51. 



t Istituz. di Notom. e Fisiolog. comp. t. i. p. 278. 



^Lehrbuch der Zootomie. 



II Malacologie, 157. 



H Uber die Teichmuschel, p. 10. 

 * Edin. Med. and Surg. Journal, vol. xxxiv. 

 ft Tom. xi. p. 182. 



Nova Acta Acad. Caes. Lcop. xvi. p. 58, scq. 

 | Loc. cit. 



