193 



I am of the opinion that Tretjakoff's category of amacrine cells 

 rests upon faulty impregnation or failure to recognize the axones, or 

 both. This is strongly indicated by the following statement in the 

 description of the tectum opticum: "Echte Nervenfortsätze habe ich 

 auf keine Weise färben können ; soviel aus den Präparaten nach Ramon 

 Y Cajal geurteilt werden kann, werden im Tectum von Ammocoetes 

 überhaupt keine aus ihm heraustretenden Projektionsbahnen gebildet" 

 (p. 686). The fact that he had no axones impregnated in the whole 

 tectum opticum should have led the author to suspect that his pre- 

 parations were unreliable for the study of the origin of nerve fibers 

 in other parts of the nervous system. In the tectum opticum of the 

 adult Tretjakoff has succeeded in staining the axones in some cases. 

 Whatever may prove to be true regarding amacrine cells in the brain 

 of Ammocoetes, it is clear to the writer that no opinion as to their 

 existence should be based on preparations in which a whole center 

 like the tectum opticum appears to be made up of cells devoid of 

 axones. 



The writer has presented on several occasions a system of func- 

 tional divisions of the central and peripheral nervous system as a 

 valuable method of investigation (1902 a, 1906, 1909). Time has fully 

 justified the statement made in 1902 (p. 1111): "Es ist offenbar, daß 

 die Anerkennung dieser Funktionsglieder eine bessere Methode zur 

 Beschreibung des Gehirns an die Hand gibt als die bisher gebrauchten 

 rein anatomischen oder architektonischen Methoden, und daß sie auch 

 eine wertvolle Unterstützung für fernere Untersuchungen sein werden. 



Die Analyse des Nervensystems auf Grund von Bau und 



Funktion ermöghcht ein vollständiges Schema, das sowohl als Führer 

 bei der Untersuchung wie als Methode für eine Beschreibung unent- 

 behrlich ist." With this schema of functional systems so completely 

 worked out as it has been in nearly all classes of vertebrates every 

 worker has ready to his hand the means of critically interpreting his 

 preparations with reference to the general paradigm of organization 

 of the brain, at least in the region of the cranial nerves. There is 

 no excuse for any author publishing a description of a brain in which 

 a whole functional system has been overlooked. The paper by Tret- 

 jakoff, through his failure to recognize the visceral sensory system 

 and his failure to reach an intelligent analysis of the gray columns in 

 the brain illustrates admirably what is lost through the lack of a ge- 

 neral guiding principle in research. 



Anat. Anz. XXXVII. Aufsätze. 13 



