412 APPENDIX. 



described by M. Ascherson, because they are not situated in the median line of the 

 body ; and as they have no communication with the air-passages, we must necessa- 

 rily infer that their origin is not similar. He is of opinion that they should be re- 

 garded as proceeding from some anomaly or aberration of the nisus formativus, 

 congeneral with those which cause an arrest of the development of the foetus, during 

 one of those phases which it successively passes through, before it reaches its perfect 

 state. To one of these transition forms belong the branchial fistula; discovered by 

 Rathke, first in the young of the pig, horse, hen, water-snake, (coluber natrix) and 

 lizard, and afterwards in a human embryo, about seven or eight weeks old. These 

 fistula; or tubes consist in from six to eight apertures, arranged symmetrically on 

 either' side of the neck, opening into the pharynx, covered externally with a sort of 

 operculum, and exhibiting on their inner surface several arched lamellae. Rathke 

 compares these apertures with the branchial apertures of the shark ; and a beauti- 

 ful confirmation of this opinion may be derived from the identity which exists in the 

 vascular arrangements of fishes and of the early chick, as clearly made out and de- 

 scribed by M. Huschke of Dresden. This anatomist publicly demonstrated that the 

 aorta of the young chick gives off six branches, which pass on to the inner surface 

 of the branchial arches, (or those lamellae which are considered as rudimentary bran- 

 chiae), and which afterwards communicate with, and terminate in, the descending 

 aorta. Biiar has verified the existence of these branchial apertures in the foetal dog 

 and rabbit ; and his observations have been confirmed by Burbach, Muller, Allan, 

 Thompson, and Becker. M. Rudolphi mentions having seen at Stralsund, an infant in 

 whom the closing up of a fistula of this sort, brought on aphonia, epileptic convulsions, 

 and other alarming symptoms, which gave way only when the ulcer was re-established, 

 and the discharge permitted to flow. In one of the cases related by Dzondi, the 

 healing of the fistulous opening was followed by a train of evils which finally proved 

 fatal. 



END OF VOL.II. 



LONDON: 



J. HENDERSON, PRINTER, 

 WHITE-FRTARS. 



Li- •'' 



' 



