STUDIES or THE MA.CllOCnillES. 



381 



into four distinct muscles, but rather to resemble that of the Fly- 

 catchers, although nothing certain can be stated on this point." 

 My own investigations upon other species than T. colubris go 

 towards establishing in the main this admirable description of a 

 very painstakiiig anatomist, for whom I have always entertained 

 the highest regard both for his character and his work. It is 

 needless to add that such a trachea, the counterpart of which is 

 seen only in the Spoonbill, is sufficiently far removed from the 

 form it assumes in the Cypseli to satisfy the most sceptical as 

 to any affinity on that point ! In Swifts it does bifurcate " at the 

 usual place ; " it possesses but two pairs of muscles (the lateral 

 ones, and those that go to the sternum), and in all other points 

 is widely and fundamentally at variance with the windpipe and 

 bronchi of the Trochili. 



Careful as Mac Grillivr ay's account is, however, he neglected 

 to mention one very important difference, so far as these parts 

 are concerned in the birds under consideration, and that is, the 

 Trochili constitute one of those rare groups which lack the pair 

 of sterno-tracheales muscles ; I carefully searched for them in 

 several species of Humming-birds, but failed to find them, and 

 am quite convinced they do not exist. 



If the reader will kindly turn to figure 33 of Plate XXIII. 

 illustrating this memoir, he will find my drawing of the trachea 

 of a Humming-bird, and in figure 35 the position it occupies in 

 the thorax and neck with respect to the other organs. 



Indeed, in figures 35 and 36 I have drawn the bodies of a 

 Humming-bird and a Swift, after having carefully removed the 

 pectoral muscles and sternum, in order to show this very thing. 

 A glance at these two figures will be sufficient to satisfy any one 

 as to the remarkable difi'erence they present. In the Humming- 

 bird, we are struck at once by the position of the trachea ; the 

 direct course of the left carotid, the enormous heart, and the fact 

 that the low position of the liver conceals from our sight all the 

 other viscera harboured in the abdominal cavity. Here, as in 

 most birds, the right lobe of the liver is the larger of the two, 

 which in the Humming-bird, as we see, curls round the apex of the 

 heart (more so in T. platycercus), modelling itself to that extre- 

 mity of it. Still more at variance, as compared with the Swaft, 

 is the digestive tract of a Humming-bird, for, so far as I am fami- 

 liar with the morphology of the group, in none of them do I know 

 of a species winch possesses, as compared with the size of its 

 intestines, so exceedingly small a stomach ! This organ, together 



29* 



