and the Muscular Structure of Cilia. 169 



little muscles. He now wrote a fresh paper, containing an 

 account of his renewed researches on muscle and of the 

 muscular character of cilia. Purkinje translated that paper 

 into German and communicated it to Muller's Archiv, where 

 it occupies sixty-eight pages 8vo, with numerous engravings. 

 Although we cannot, from the number of the engravings, give 

 this very valuable contribution to science a place in our 

 Journal, we embrace this opportunity of recommending it to 

 the particular attention of naturalists. They will find in it 

 a confirmation of Dr Barry's observations published nine 

 years ago, " that the structure of muscle is a spiral struc- 

 ture," and discover (not published before) that cilia have 

 a truly muscular character and structure ; this being de- 

 monstrable, not only in cilia from the gill of the oyster and 

 the common sea mussel, but in those of the Infusoria. (But 

 of course if any cilia are muscular, all cilia are so.) 



Letter from Mr Stevenson Macadam to Professor Jameson, on 

 M. Chatin! s Observations on the General Distribution of Iodine. 



Philosophical Institution, 

 Edinburgh, 22d June 1852. 



Dear Sir, — A short time ago M. Chatin read a memoir 

 before the French Academy of Sciences, in which he stated 

 that he had detected the presence of iodine in the atmosphere, 

 in rain-water, in soils, &c. His observations led him to 

 believe that the greater or less quantity of iodine present in 

 any one district, to a certain extent determined the presence 

 or absence of goitre and cretinism. With the view to corro- 

 borate, so far as possible, the results announced by M. Chatin, 

 I have, this summer, undertaken a series of analyses in refer- 

 ence to the general distribution of the important element in 

 question. 



I am not aware that Chatin has published a detailed 

 statement of the processes which he pursued, or the reagents 

 which he employed in his experiments ; but from the mention 

 which he makes of the good offices fulfilled by potash in arrest- 

 ing " the complete decomposition of the iodine compounds pre- 

 sent in water," and by carbonate of potash and carbonate of soda, 



