[ 177 ] 



XXVI. Renewed Inquiries concerning the Spiral Structure of 

 Muscle, with Observations on the Muscularity of Cilia. By 

 Martin Barry, M.D., F.R.S. 



[Concluded from p. 9S.'\ 

 On the Muscularity of Cilia. 



AS his previous observations had led him to expect, cilia were 

 found to be no other than his twin or double spirals. No 

 man, he thinks, will do him the injustice to suppose he maintains 

 the possibility of discerning- a double spiral in the miimtest cilium. 

 He is as far from maintaining this as he is from asserting the 

 possibihty of seeing a double spiral in the minutest muscular 

 fibril. But he does maintain that those who undertake the 

 examination of cilia in the way in which they should set about 

 the examination of all organic tissues, i. e. with a desire to know 

 how they originate, what is the history of their development, 

 will certainly find that the double spiral is the fundamental form 

 of all cilia the structure of which can be reached with the micro- 

 scope, and therefore probably of the most minute. Indeed under 

 favourable circumstances, traces thereof are not so very rarely to 

 be discerned, by the accustomed eye, even in the latter. 



In the author's observations he used several bivalve moilusca, 

 including the Oyster, Ostrea edulis, and the common Sea Mussel, 

 Mytilus edulis. The one last mentioned is to be preferred, 

 because of the bars of its branchial laminse being most easy of 

 separation. And this mussel is further recommended to those 

 disposed to rej^eat the author's observations, on account of the 

 excellent description of its gills given by Dr. Sharpey in his 

 Article " Cilia ■" in Todd's Cyclopaedia of Anatomy and Physio- 

 logy. He recommends the examination of this Mussel when 

 small, because of the branchial laminae being more transparent 

 than in the larger specimens. He examined some in which the 

 shell measured scarcely two lines in length, they being the small- 

 est he could obtain. The most convenient size, however, he 

 found to be that in which the shell measured in length from ^ 

 to I of an inch. Still an examination of the largest should not 

 be omitted. 



Convinced by his earlier microscopic labours that it is best to 

 direct the eye for a considerable time exclusively to the same 

 part or set of objects in order to enable it to detect minute dif- 

 ferences in the same or in different individuals, the author 

 directed his solely to the branchial laminaj, and here to little 

 more than the sides of those ])arallel bars of which the branchial 

 laminae are composed. In this way it was that he became ac- 

 quainted with the fact, that, as the ever-acting heart requires a 

 continued renewal of its fibrils, so are new generations continu- 

 ally preparing to succeed the indefatigably vibrating cilia. 



Phil. Mag, S. 4. Vol. 4. No. 24. Sept, 1852. N 



