OCR Text |
Show 1878.] TRACHEA OF RHYNCH.EA CAPENSIS. 751 greatly expanded and produced backwards, so as to form by their fusion in the middle line a broad, flat, and squarish plate of bone strongly bilobed and tipped with cartilage at the hinder extremity, into which ossification extends with advancing age, rendering the posterior angles of the plate prominent, and bringing them into very loose relation of apposition with the much less expanded ventral ends of the second pair of bronchial half-rings ; the ovoid saccular dilatations seen in figs. 3 and 4 result partly from the inflation of the membrane interposed between the ends of these half-rings and the posterior angles of the three-way piece, but principally from that of the ventral halves of the membranous inner walls of the second and third pairs of bronchial half-rings. The spatulate dorsal ends of the first pair of bronchial half-rings do not meet in the middle line, but curve inwards and backwards so as to leave between them a membranous interval, into which a narrow tongue of bone projects from the middle of the posterior margin of the last tracheal ring. In so small a figure no distinction between bone and cartilage in the three-way piece was possible. Drawn from a fresh specimen by Behari Lai Dos. Fig. 2. A much enlarged view of a portion of the same, to show the form the modified part of the tube assumes when it is naturally expanded ; the constricted portion (a) presents a singularly finely and regularly ribbed appearance, being composed of about forty very fine and closely packed cylindrical rings, all firmly bound together so as to form a stiff but still somewhat elastic mass. Fig. 3. A much magnified ventral view of the posterioi' end of the same, to show the inflated condition of the membrane connecting the compound three-way piece with the second (apparent first) bronchial half-ring on each side, and also the two egg-shaped saccular dilatations (e, e) of the membranous inner walls of the bronchi. Fig. 4. The same, from the left side, to show the egg-shaped dilatations (e, e) in profile, and the thin and narrow lateral slip of muscle (I) which is attached to the three-way piece at m, whence some of its fibres pass on to the second bronchial half-ring (n). (All the three preceding figures were drawn under the microscope by the aid of a camera lucida, immediately after the death of the animal.) Fig. 5. The complete trachea of an immature female, nat. size. The two sterno-tracheal muscles (st.t, st.t) are seen to be blended on the ventral surface of the constricted portion of the tube at a ; I, I, are the lateral muscles, somewhat exaggerated in the drawing. Drawn by B. L. D. Pig. 6. The posterior portion of the unmodified windpipe of an adult male, nat. size. The lateral muscles (I, 1) are here so pale and transparent as to be all but undistinguishable in the fresh state. Fig. 7- The same, much enlarged. (With the two exceptions above mentioned, the figures of this plate have been obligingly drawn for m e by Lieut.-Col. H . H . Godwin- Austen, by w h o m also the plate has been lithographed. The following paper was read on June 4th, but was necessarily omitted from its proper place in consequence of the illustrations not having been finished in time:- |