187H.] TRACHEA OF RHVNCH^A 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 membra- 

 nous 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 closelv 

 packed cylindrical rings, all firmly bound together so as to form ii 

 stiff' but still somewhat elastic mass. 



Fig. 3. A much magnified ventral view of the posterior 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 §ide, 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 («). 



(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. 



Fig. 6. The posterior portion of the unmodified windpipe of an adult male, 

 nat. size. The lateral muscles (I, I) 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 me by Lieut.-Col. H. H. God- 

 win-Austen, by whom 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 : — 



