July 1, 1S69.J 



HARDWICKE'S SCIENCE-GOSSIP. 



149 



the central branchial tube escapes by the oesopha- 

 gus, inasmuch as careful dissections made by a 

 skilled anatomist within the last few days in my 

 presence, disclosed two cartilaginous epiglottidian 

 valves (o, Fig. 115) guarding the upper extremity of 

 this central respiratory channel and effectually pre- 

 venting regurgitation ; when the gill-chambers, and 

 the said channel were iujected through the external 

 openings, the water with which the whole respira- 

 tory system was fully distended could not be forced 

 out into the mouth. The central tube, which is of a 

 flattened form, having its vertical diameter the 

 greater, appears to be a pump used both for sucking 

 water in and to aid in forcing it out. 



Although Cuvier had declared that the popular 

 belief that water passed through the nostril into the 

 branchial channel was unfounded, and Sir Everard 

 Home in more recent times had shown the suppo- 

 sition to be erroneous, while Huxley in our own 

 day speaks of the olfactory passage as ending in a 

 cacum or blind sac, we still find the old mistaken 

 notion perpetually reproduced. A writer of note, for 

 example, tells us " there is another remarkable ar- 

 rangement in the Lampreys: this consists in the 

 presence of a small tubular orifice situated in the 

 middle of the back of the head just in front of the 

 eyes, which leads downwards into the pharynx, into 

 which it opens by the orifice (c, Pig. 114), so that 

 water can enter this passage while the mouth is 

 kept immovably fixed to the surface whereunto the 

 Lamprey has attached itself " ; another has actually 

 made " an aperture on the top of the head com- 

 municating with the gills," one of his characteristics 

 of the Petromyzonickc, in defiance of all previous 

 testimony ; it is in the Myxinoid fishes, and not in 

 the Petromijzvnida, that this aperture communicates 

 with the gills; this difference of construction consti- 

 tuting one of the generic distinctions between them. 

 The Berseans of old were held to be more noble 

 than the men of Thessalonica because they searched 

 to see for themselves "if these things were so," an 

 example which all students, especially students of 

 Natural History, will do well to follow. 



Notwithstanding the preponderating mass of 

 evidence in proof of the nasal tube having nothing 

 whatever to do with conveying water to the breath- 

 ing apparatus, it was chiefly to satisfy ourselves on 

 this particular point that a number of special 

 dissections were undertaken. The nostril is not 

 correctly described as " an aperture " merely ; a 

 stiff tube of the size and somewhat the appearance 

 of a goose-quill projects above the general surface 

 just in front of the eyes ; before the knife was taken 

 in hand, the blowpipe first, and then injections, 

 were used to ascertain if the olfactory orifice ended 

 in a true ctscum, or possessed any valve or outlet of 

 any description communicating with the mouth 

 pharynx or branchial chamber ; the results, as well 

 as the revelations of the scalpel, proved to demon- 



stration that the nostril ends posteriorly in an im- 

 perforate caecum, and has nothing on earth to do 

 with the respiratory system. 



In Pig. 115 (a, a) show the vertical sections of 

 the oral ring ; (b and c) are cartilaginous plates, 

 attached by muscles and ligaments hanging in loose 

 folds when the mouth is closed, the plates sliding 

 over each other to admit of the wide expansion of 

 the mouth when opened out in a vertical circle for 

 suctorial purposes : one complete lip (the right) and 

 border of the mouth is shown in the natural position 

 it rests in when the mouth is closed. It may be 

 traced in the engraving from the tip of the snout, 

 its margin folding slightly over inwards, the inner 

 edge of the lip bearing a zone of three rows of soft 

 papilla} (t), apparently the rudiments of teeth which 

 never acquire the hard covering, to (m) where a 

 deep commissural fold is formed. When the mouth 

 is opened wide, the tip of the snout is thrown 

 upwards and backwards nearly as far as the point 

 (b), the lower angle of the lip (m) is thrown 

 forwards nearly to the point (/), the entire oral ring 

 is thus made vertical, and widely expanded : it can" 

 easily be understood how after the lips (when the 

 mouth is in this position) are applied to a surface, if 

 the powerful piston-like tongue which closes the 

 throat be drawn backwards, a complete vacuum is 

 formed in the cavity of the mouth, and it does not 

 surprise one to hear that Lampreys after they have 

 paired remove stones from the bed of their spawn- 

 ing places, and when dragged out of the water, tail 

 foremost, have in some instances brought with them 

 a block of stone twelve or fourteen pounds in 

 weight. 



The soft fibrous basis of the lip is shown in 

 section at (r) ; (a) marks the hard cartilage of the 

 oral ring; (b and c) show the imbricated plates 

 sometimes spoken of collectively as "the hard 

 palate," the larger plate of the two denoted by (c) 

 is the " ethmo-vomerine plate " of Huxley : next 

 comes the much talked of nasal orifice, which 

 appears to be unprovided with any valve or guard 

 to prevent foreign bodies from entering the passage 

 (d) which leads into the olfactory capsule (e), the 

 seat of the sense, which is lined with a black pig- 

 ment, and supplied with nerves spreading over its 

 surface. 



" Between the basi-occipital plate of cartilage and 

 the hard palate there is an oval space through 

 which the neck of the long olfactory caecum passes ; 

 this caecum therefore separates the front part of the 

 floor of the cranial cavity, which is simply membra- 

 nous, from the so-called hard-palate " ; the con- 

 stricted " neck " is clearly shown in our figure, and 

 the entire canal can be traced by the reader from 

 the inlet to the fundus of the blind bag (g). The 

 use of this narrow-necked canal with its wide 

 dilatable pouch (g) is sufficiently evident. The 

 external orifice of the olfactory tube being 



