THE VESSELS. 33 



without affirming that the spire is tubular, believes that 

 it approaches the cylindrical form ; and as for myself, it 

 appears to me fiat, with the two borders more or less 

 opaque and probably a little prominent (PI. 2, fig. 4). 



3d. Is the spire of the trachea contained in a parti- 

 cular tube, as Bernhardt would have us think ? — I 

 believe that we cannot deny the existence of this tube, 

 but it is necessary to know whether it is one which 

 might be formed by the edges of neighbouring organs, 

 or whether it is a part of the trachea. Dutrochet 

 admits the existence of a tubular membrane, which is 

 not on the outside of the spires, but between them. 

 The existence of a membrane which would unite the 

 spires together, appears confirmed by the existence of 

 tracheas which are incapable of being unrolled, men- 

 tioned by some authors ; but they have never been seen 

 in a clear manner, and probably they are nothing more 

 than annular vessels, of which we shall speak hereafter. 



According to Mirbel, the trachese are continuous 

 with the cellular tissue by their extremities ; according 

 to Dutrochet, they terminate, by their two extremities, 

 in a very acute conical spu'e. 



The spires of the trachese, according to Hales, are 

 always rolled from right to left ; this disposition appears, 

 in fact, the most common, but Link has remarked some 

 which were rolled from left to right. 



Mirbel, Rudolphi, and Kieser, have discovered some 

 trachese with a double and triple parallel spire ; I 

 have counted some even with seven in the tracheae of the 

 Plantain (Musa paradisiaca,) PI. 2. fig. 3 ; and M. De 

 la Chesnaye says that he has counted up to twenty- 

 two. Rudolphi says that the tracheas also have a 

 doubled, or a multiphed spire, in Canna, Amomum, 

 Kcempferia, Maranta — genera all allied to Musa ; and 

 even, he says, in Heracleum speciosum, which belonos 



VOL. I. D 



