16 REPORT OF THE SECRETARY. 



paper, by S. Weir Mitchell, M. D., and George R. Morehouse, M. D., 

 of Philadelphia, is a very complete study of the anatomy and physi- 

 ology of the breathing organs in turtles. It seems that, although at 

 one time, and by a single observer, tlie true mode of the breathing 

 of these animals was partially understood, it had long been neglected, 

 and modern physiologists have taught that turtles forced air into the 

 lunjzs as do frogs. Drs. Mitchell and Morehouse have shown that 

 turtles breathe like mammals, by drawing air into the lungs by the 

 akl of muscles situated in the flanks and on the outside of the lungs. 

 Their paper contains a detailed account of the anatomy of the breath- 

 ing organs of turtles, and is illustrated with numerous wood-cuts. 

 The most novel discovery described by the authors is that of a chiasm 

 or crossing from side to side of a portion of the nerves which supply 

 the muscles of the larynx. Except the well-known facts as to similar 

 crossings within the skull, no previous author has described any simi- 

 lar extra-cranial arrangement of nerves. The physiological uses of 

 the laryngeal chiasm has been fully studied by Drs. Mitchell and 

 Morehouse ; and more recently Professor Wyman, led by their dis- 

 covery, has described similar nerve arrangements in serpents and in 

 certain birds. 



The authors express their indebtedness to the Smithsonian Insti- 

 tution for the aid with which they were furnished in obtaining the 

 requisite specimens for experiments and for dissection. 



The following papers have been accepted for publication, and will 

 form parts of the fourteenth volume of Contributions : 



Ist. Three additional parts of the series of discussion of the mag- 

 netic observations at Girard College, by Professor A. D. Bache. 



2d. The result of a series of microsco'pical studies of the medulla 

 oblongata, or the upper portion of the spinal marrow, by Dr. John 

 Dean. 



3d. A memoir on the palaeontology of the Upper Missouri, by F. B. 

 Meek and F. V. Hayden. 



4th. An account of the photographical observatory and various 

 experiments in regard to this subject, by Dr. Henry Draper, of New 

 York. 



5th. A monograph of the "Laridas" or gulls, by Dr. Elliott Coues. 



All these memoirs, except the last, are in the hands of the printer, 

 or in process of illustration by the engraver. 



In several of the preceding reports an account has been given of a 

 series of reductions of the magnetic observations made from 1840 to 

 1845, inclusive, at Girard* College, Philadelphia, by Professor Bache. 



