398 ELECTRO-PHYSIOLOGY CHAP. 



cylinders surrounding the trunk on either side, and these 

 represent the single, albeit bilaterally symmetrical, electrical 

 organ, the weight of which, according to Fritsch, is more than 

 one -third of the total body -weight. "Anteriorly it extends 

 laterally as far as the pectoral fin, superiorly in a lobe-like 

 prolongation to the region between the eyes, inferiorly to the 

 anterior wall of the shoulder-girdle. Posteriorly ; above to the 

 origin of the dorsal fin, below to the origin of the anal fin." The 

 diameter is greatest in the centre of the trunk, and a little in 

 front of this, and gradually diminishes towards the anterior and 

 posterior ends of the body. 



The complete integrity of the system of skeletal muscles, both 

 anatomically and as compared with all other electrical fishes, is 

 very remarkable, and causes Fritsch to assume that the electrical 

 organ has not in this case been differentiated from the muscles. 

 Since it here arises wholly from elements of the skin, its struc- 

 ture must be described in detail. 



Under the lens (Fritsch, 1 2 /) the wealth of small conical 

 villi is especially remarkable, between the bases of which there 

 are rounded openings leading into tubular pits in the epithelium. 

 Around these there is a crowd of binuclear " club-cells " (Fig. 

 259), which function as unicellular glands, and are well developed 

 from below, like those found in the skin of other fishes ; these 

 finally empty their contents into the adjacent epidermoid tubes. 

 But in this case a special interest attaches to the club-cells, since 

 Fritsch ascribes to them conjecturally " the same embryonic 

 arrangement as the elements of the electrical organ." As we 

 are completely ignorant of the ontogenesis of the latter, this is 

 only a hypothesis, and must be left over for future investigation. 

 It should be no matter of surprise if the elements (unicellular 

 glands) next in electromotive activity to muscle were to prove 

 capable of forming true electrical organs. For the rest, the epi- 

 dermis of Malapterurus consists of ordinary epithelial cells (bristle 

 or prickle cells) and a few goblet cells, i.e. on the side of the villi. 

 As regards the finer structure of the organ, the first point that 

 strikes one is the lack of any regular arrangement of the plates 

 into " columns," as in Grymnotus and Torpedo.. Nor can the 

 brawn-like mass deposited from the skin of Malapterurus, and 

 similar in consistency, when fresh, to the vitreous body, or to 

 Wharton's salts, be compared with the imperfect electrical 



