January 4, 1894] 



NA TURE 



223 



^vord about that divergence. I spent much time in count 

 ing the elements in the organ of Torpedo, and confirmed 

 rny results by counting also the ganglionic cells belong- 

 ing to the plates. My total comes very near to that of 

 Valentin, but amounts only to 179,625 in each organ. 



Prof. Ewart cannot expect me to give up my number 

 in favour of his, published much later, before he proves 

 that I made a wrong estimate. He speaks also of the 

 large Torpedo of America, and calls it Torpedo giganiea. 

 It seems he is not aware of the fact that the name of 

 Torpedo gignntca is given to the petrified species from 

 the Monte Bolca, whilst the American species got the 

 name of T. oca'deniaiis {Stoxer). He ignores, or neglects, 

 at the same time, the fact that a near related species, 

 which has about the same number of electric elements, 

 generally named T. iwbiliajia (Bonap.), occurs also in the 

 British seas. 



If it is difficult to explain such want of harmony with 

 other authors ; it amounts to an impossibility for a 

 foreigner to give a clear account of the following papers 

 concerning the cranial nerves of Elasmobranch fishes. 

 Not that I mean to blame my learned colleague for this ; 

 on the contrary, I admire the papers very much, and re- 

 commend them with all my heart to everyone who wants 

 instruction about the finer details of these nerves ; but 

 with regard to the nomenclature employed. I am afraid 

 very few continental authors will agree with the 

 homologies stated by Ewart. When he in a certain 

 place says against Sappey, " that nerve is all but uni- 

 versally acknowledged to be a part of the facial,'' Sappey 

 will most decidedly state " that nerve is all but universally 

 acknowledged to be a part of the trigeminal." 



Considering it of little use to discuss the confusion of 

 names in the papers quoted by Ewart, I wish it to be 

 borne in mind that the leading principle of the author to 

 prove his homologies is the equality of distribution of the 

 ner\-es in the peripheric organs. If that holds good, as 

 I am convinced it does, how can he at the same time 

 give the name of a true motor nerve (A', facialis) to a 

 cephalic nerve of a true sensitive character .' Perhaps he 

 will answer, " All, or at least most, of the other authors 

 do, why shouldn't I do the same.'" Putting aside the 

 protest many continental authors (myself included) make 

 against such nomenclature, at any rate his principle of 

 innervation is given up, and I am firmly convinced that the 

 comedy of errors in the nomination of cranial nerves in 

 comparative anatomy will not cease until quite new 

 names or, perhaps still better, only numbers are applied 

 to them according to the place of origin in the substance 

 of the central nervous system. Motor and sensitive 

 nerves must be kept separated by all means, segmental 

 and not segmental nerves may be designated at tlie same 

 time in any proper way. 



It is in this respect that the want of an international 

 understanding is most severely felt, and we must hope 

 that the future may provide an advancement of science 

 also in the matter ; for before a firm and clear base for 

 these homologies of nerves is given, we might just as well 

 talk Chinese toge her. 



Professor Ewart's investigations about the cranial 

 nerves had for their chief purpose a clearer insight into 

 the innervation of certain organs of sense, treated 

 in another paper annexed to the same volume. I am 

 very glad to state that the impossibility of accepting his 

 homologies does not interfere with his results as regards 

 the innervation of these sense organs. 



The anatomical skill of the author is best shown in 

 the treatment of the structure of these organs. So far 

 as my own experience in these matters goes, I am led to 

 ask, Are his statements and figures of the sensory canals 

 and the nerves belonging to them very correct and com- 

 plete ? He overreaches the previous writers treating the 

 same objects by the adm.irable finish of his papers 



NO. 1262, VOL. 4q] 



which, as far as I see, ought to be followed by another 

 concerning the ampullaiy canals. 



In this chapter I have also to object to his way of 

 treating the literature and of stating homologies in spite 

 of his own principles. 



The sense organs 1 discovered on the skin of Raja, and 

 called " .Spaltpapillen," named " pit-organs " by Ewart, 

 were not found by any other author before. It is not 

 true that Merkel saw them on the back of Mustelus and 

 at the mouth of Spatina ; he described only " freie Ner- 

 venhugel" {free nervous collines) in these places. The 

 name itself proves that the sense organs described by 

 Merkel belong to another group altogether, and so does 

 their position. 



How Ewart, who places such importance in the distri- 

 bution of the nerves, can find that the " Spaltpapillen" 

 probably correspond to organs of Squatina placed at the 

 mouth of a very different make and different innervation, 

 he may know himself, but the reader finds it impossible 

 to follow such argument. 



The figure he gives of the pit-organ (sensory canals, 

 pi. 3, Fig. 10) does not show such an organ fully deve- 

 loped. Otherwise the split would be narrow and straight, 

 the cells by which it is lined flattened and columnar, not 

 rounded, the papilla itself much higher raised above the 

 surface of the epithelium, and pigment cells frequently 

 found between the epithelial ceils. (Comp. my paper: 

 " Uber Bau und Bedeutung der Canalsysteme unter der 

 Haut der Selachier." Sitz. Ber. d. Berlin Akad. d. 

 Wischenss^ 1888, s. 291.) 



The papilla is, in the adult, a good deal raised above 

 the level of the skin, so that even the sense organ at the 

 bottom of the split in the papilla has still a somewhat ele- 

 vated position. This position prevents me from admir- 

 ing the name of "pit-organs," as a pit ought to mark a 

 depression below the main level. Continental writers 

 will also shake their heads in reading that a differen- 

 tiated group of epithelial cells forming a sense organ, and 

 resting between them, is called a " follicle," which by 

 all means wants a kind of stronger envelope enclosing 

 the cells. But I quite agree that in England Latin 

 words might be admitted, which would not do on the 

 continent. 



Before Prof. Ewart proceeds to describe the am- 

 pullary canals, I recommend him once more to study 

 the paper of Savi concerning these canals. He places 

 the French author amongst those who take also the am- 

 pullary canals for sense organs, which is a great mis- 

 take, as Savi affirms in most decided terms the 

 excretoric function of the ampullary canals. (Mateucci 

 et Savi, " Etudes Anatomiques sur le Systeme Nerveux et 

 sur rOrgane Electrique de la Torpille," p. 331.) 



But such objections very slightly detract from the 

 great merit of the author. They only prove the strong 

 interest which the perusal of Prof. Ewart's papers has 

 aroused in me, as it will do in all other readers. 

 I cannot conclude my remarks without acknowledging 

 once more, with all my heart, the magnificent results ob- 

 tained by him, and I trust that he may succeed further 

 in the same direction. Gustav Fritsch. 



NAVIGATION BY SEMI-AZIMUTHS} 



THE year 1893 should be an interesting one to 

 nautical men. A new Daniel has come to judg- 

 ment in the person of Mr. Ernest Wentworth Buller, 

 M.R.A.I., M.R.U.S.I.,M.I.E.E., the inventor of the semi- 

 azimuth system of navigation, who is equally earnest in 

 denouncing the shortcomings of the existing systems of 



1 "Semi-Azimuths. New Method of Navigation, being a combination 

 of Spherical Trigonometry and Mercator's Sailing." (London: Norie and 

 Wilson, 1893.) 



