OCR Text |
Show 524 MR A. H. GARROD ON THE [June 5, rings are incomplete opposite the processus vocales (in other words, at their sides), as they are in all the Tracheophonse; and the lowest is also broken, as it were, in the middle line behind. Posteriorly the lower nine are extremely slender; the tenth (counting upwards) is somewhat thicker, the eleventh still more evidently so, whilst the twelfth is as thick as any of the superior rings. Anteriorly there are twenty-three of the lower tracheal rings, which are quite slender in the middle line, especially the lowest three ; and of these the twelve lowest (those split laterally) are slender from one side to the other, whilst the upper eleven appear thick at their extreme ends on account of the intrusion, for a short distance round the sides of the tracheal tube, of the thickening above recorded of their hinder parts, which diminishes rapidly in a spindle-pointed manner. The lowest tracheal ring is as slender as those just above it; and it is worthy of note that the processus vocales rest upon the thickened second bronchial semi-ring as well as on the first. These vocal processes cannot be detached from the sides of the trachea without injuring it; and the sterno-tracheal muscles arise from their apices, to which are also attached thin muscular sheets which extend up the windpipe laterally and a little posteriorly. Grallaria guatemalensis.-In this species also the specialized syrinx does not cease abruptly at its upper end, the superior rings of the trachea, which help to constitute it, gradually losing their individual character. Figs. 1 and 2 (Plate LIII.) represent the front and back view of the organ, which is peculiarly shallow for its width, and involves but six of the lowermost tracheal rings. These six are incomplete at their sides where they are in contact with the processus vocales, which latter are small, flat, fusiform ossifications, pointed both at their upper and lower ends, and just touch the upper of the two superior enlarged and ossified bronchial semi-rings, the remainder of each bronchus being of the normal character. The lowermost tracheal is incomplete in the middle line in front, as well as at the sides, whilst behind it is thickened, and sends small downward processes on each side of the middle line in such a manner as to develop a notch between them. Figure 3 represents the left-side view of these structures, seen from the interior of the organ, a being the processus vocalis. From figure 1 it can be seen that the tracheal rings four, five, and six from the bottom are not ossified at all in front, and that rings seven, eight, and nine are only so at their sides, whilst ring ten, with those just above it, are extremely thin in the middle. Posteriorly also, from figure 2 it can be inferred that the rings above the bottom ones are very slender, becoming thicker by degrees above the sixth, which is the highest of those constituting the voice-organ. With reference to the muscles, it m a y be stated that the lateral muscle of the trachea on each side covers and joins the upper extremity of the processus vocalis, turning off to become the musculus sterno-trachealis opposite the ring third from the end, and sending no continuation on to act directly upon the bronchial semi-rings. |