The finer Structure of the Nerve Cells of Invertebrates. 25 



irregular in form or round. Pflücke does not regard these structures 

 as free and independent granules, in the same sense as Altmann, 

 but figures them as being connected with each other by means of 

 fine thread-like fibrils. He says: "Es unterliegt also keinem Zweifel 

 mehr, dass wir es hier mit nichts anderem als mit längern oder kurzem 

 Theilstücken von Fäden zu thun haben, Fäden, die in ihrem Verlauf 

 von Strecke zu Strecke spindelförmige Verdickungen tragen" (p. 516). 

 These fibrillar thickenings are found by him chiefly in the cell 

 body, and extend only for a short distance in the cell process. ^ The 

 fibrils, which in the cell process run parallel to its long axis, continue 

 in the same general direction as isolated fibrils in the ectoplasmatic 

 area of the cell, but in the centre of the cell anastomose to form a 

 network. He says further: "Ueberblicken wir nun noch einmal die 

 Verhältnisse, so müssen wir schliessen, dass die Fibrillen bei Eintritt 

 in die centrale Masse der Zellsubstanz ihren isolirten Verlauf auf- 

 geben, durch zahlreiche Queranastomosen ein ausgeprägtes Netzwerk 

 bilden, dessen der Kernwand zunächst gelegene Knotenpunkte radiäre 

 Fädchen zur Kernmembran hinübersenden und in den Verdickungs- 

 stellen der letztern mit den Endbälkchen des Kerngerüstes ver- 

 schmelzen" (p. 518). 



For the results obtained by Lugaro (20), I insert a quotation 

 from Herrick's review of the same ^). 



"Nissl's method of differential staining after alcohol hardening, 

 which has given such an impulse to recent cytological work, is made 

 the basis of an investigation of the relative functional value of the 

 chromatic and the achromatic elements of the general protoplasm of 

 the nerve cells. Dr. Lugaro comes to the conclusion that the achro- 

 matic substance is the physiologically active medium, while the chro- 

 matic elements are simply passive. The achromatic part is composed 

 of a filar mass in the sense of Flemming, while the chromatic part 

 which alone is stained by the method of Nlssl represents the inter- 

 filar mass, and therefore the method of Nissl is absolutely negative 

 regarding the real structure of the nerve cell." 



As his work is illustrated by nerve cells of Invertebrates as well 

 as those of Vertebrates, I infer that he recognizes in the former, the 

 existence of both granules and fibrils. 



A general perusal of the above review shows that the question 

 concerning the existence of fibrils in the nerve cells of Invertebrates, 



1) in: J. Neurology, V. 6, No. 1, 1896. 



