40 Tin; siiucrrKic ok ciiHo.Moi'iiii.p; ciii.i.s oi' iiii-: xkuvous system. 



that he refers to them as "conduits de Clolf^i-Hohngren."' Hut Rina Monti (1915, 

 p. 40) has made th(> statement that the hirge internal reticular aj^paratus corre- 

 sponds to the chondriome (/. c, to mitochondria) in the nerve-cells of mammals; to 

 (luote her own words: "II grande apparato r('tic;)huv inttM'no dal (Jolgi nelle CL'llule 

 nervose di mammiferi corrisponde aduiuiue al condrioma, conune il grande ai)parato 

 descritto dal Pensa iirllc cellule cartilaginea." If Cajal is correct in his identifica- 

 tion, it would api)ear that th(> canaliculai' api)aratus and the mitochondria are 

 identical. 1 have already discus.sed (,1U12, p. 4UUJ the older statements of Popoff 

 (1906, p. 258), Smirnow (1906, p. 153), Van Durmc (1907, p. 84), Meves (1908, 

 ]). 846), and Hoven (1910, p. 479), who are incHned to believe this to be the case. 



It is liard to see how these two views can be reconciled. I am inclined to think 

 that the well-known lack of s])ecificity of the methods of silver impregnation which 

 Pensa (1913, ]). 5()0) and Rina Monti (1915, ]>. 45) have emi)loyed are the cause of 

 the confusion. 1 do not believe that the (iolgi method can be trusted invariably 

 to demonstrate a certain structure within the cell, like the canalicular api)aratus; 

 and, for this reason, I can not accei)t unreservedly Cajal's identification of the 

 canalicular apparatus with the CJolgi apparatus. 1 agree with Duesl)erg that a more 

 precise definition of the "Apparato reticolare interno" is highly desirable, but I do 

 not agree with him in his attempt (1914, j). 37) to define it in terms of its relation 

 to the centrosome, because our knowledge of the centrosome itself is so dejjlorably 

 inadecjuate. We re(|uire. above all else, more accurate metliods before th(> matter 

 can be cleared up. 



(4) This discussion of the structure of chromophile cells may be profitably con- 

 cluded by a statement of our present knowledge of the cytoplasmic structure of 

 living nerve-cells of vertebrates not in the chromophilic condition. Mitochondria 

 unciuestionably occur and may be .seen as such in living nerve-cells even without any 

 vital stain. The Nissl .substance is usually present in solution, not in the form of 

 discrete masses as seen in fixed preparations. I believe that there is also an amor- 

 l)hous argentophilic material which (when treated by ai)propriate but very capricious 

 methods) a.s.sumes the form of fibrils. The canalicular api)aratus, like the neuro- 

 Hbrils, is an unknown (juantity in living nerve-cells, although it may l)e demonstrated 

 in fixed tissues with considerable regularity. These structures, or more correctly 

 speaking substances, are distinct and should not be confused with one another. 

 Although the mitochondria alone have a definite morphology and can usually be 

 seen in living ner\e-cells, imder ordinary conditions, with the present means at our 

 disposal, it would be arbitrary in the extreme to say that the others can never be 

 seen. Pigment, fat, lipoid, etc., may of course be seen in variable amount in living 

 nerve-cells. It is the more fundamental constituents with which we are concerned. 



The recent work in bio-chemistry, summarized l)v F. (iowland IIoi)kins ( 1913, 

 p. 663) in his jiresidential address before the Physiological Section of the British 

 Association, has, I believe, an important bearing here. The cell is regarded as a 

 dynamic system of co-existing phases in more or less stable ecjuilibrium.the condition 

 of which is altered, from moment to moment, by ))roces.'<es of oxidation, reduction, 

 desaturation, condensation, etc., which naturally result in i)hysical changes in the 

 cell, with the building-up and breaking-down of molecular aggregates which may or 



