9 2 Dr. Lath am' j EJfay on the trachea or JVind pipes ff Birds'. 



Tortoife, in the Philofophical Tran factions*. It is by means of the 

 above refources, added to the obfervations I have myielf made for a 

 number of years, that I {hall endeavour to elucidate the fubjeft as 

 far as in my powci ; and although I may not be able to determine 

 the matter with fo great a degree of precifion as might be wiilied, 

 it is more than probable that others, hereafter, will be able to com- 

 plete the ftru&urc of which I have endeavoured to lay the ground- 

 work. 



I (hall begin this effay by obferving, that in mod birds the natu- 

 ral lhape of the tmcfoa, afpera arteria, or windpipe, by all which names 

 this part is known, is that of a regularly uniform cylinder of equal 

 diameter, or nearly fo, throughout, from its rife at the root of the 

 tongue, to its entrance into the hollow of the thorax, Jlemum, or breaft- 

 bone, where it divides into two branches, called bronchi^which ramify 

 into air-veffels which compofe the two lobes of the lqags. This, 

 I fay, is the general mode of conftrudlion : but Ornithologifts pretty 

 far backf have noticed nature's deviation from this ufual ftructure, 

 both in refpect to the various curvatures of the windpipe itfelf, as 

 well as the difference of fome from others in refpecl to conforma- 

 tion ; but their fentiments were penned in too vague a manner to 

 determine much thereon, not anfwering the purpofe further than 

 to ftimulate our future refearches. As far as the deviation from a 

 cylindrical fhape is concerned, it is obfervable that the peculiar dif- 

 ference in ftruclure is feen only in the male fex, the female not having 

 the lead enlargement, or increafed cavity, as will hereafter be 

 mentioned : but to what purpofe nature has intended this, is, I be- 

 lieve, at prefent unknown to us. Some authors have given as their 

 opinion, that the enlargement of the trachea in males, whenever 



* Vol. lvi. p. 204. 



f Aldrovandus, Wiilughby.-See alfo Birch's Hid. Roy. Soc. ii. p. 13 



it 



