64 MONTROSE T. BURROWS 



protoplasm and are in no way actively influenced by the changes 

 taking place in the clot. 



The opponents of the doctrine of the independent outgrowth 

 of nerve fibres from a central neurone, as advanced by Kupffer 

 and His and so strongly supported by Cajal, Harrison and others, 

 have questioned, on grounds which need not be detailed here, 

 whether the fibres growing in lymph observed by Harrison were 

 really nerve fibres and whether they could be shown to be made 

 up of neuro-fibrillae, which take the specific stains that form the 

 basis for neurological study at the present time. 



Harrison has answered these objections in his latest paper 

 and by a full analysis of his experiments, has shown with all 

 reasonable conclusiveness that the structures in question are 

 nerve fibres, but he has nevertheless pointed out the desirability 

 of showing the identit}^ directly, by means of specific staining 

 reactions. While the present investigation was not directed 

 especially to this end, it has nevertheless been found possible to 

 obtain satisfactory permanent preparations of the artificially 

 grown nerve fibres and by means of Held's molybdic acid haema- 

 toxylin to demonstrate the neurofibrillae with remarkable clearness. 



The main purpose of the work here presented was to study the 

 movement, growth and differentiation of the embryonic tissues 

 of a warm-blooded animal and to analyze the conditions of environ- 

 ment which would stimulate or inhibit their independent de- 

 velopment. In proceeding with such an analysis, it has been found 

 necessary, as Harrison ('10) had already pointed out, so to improve 

 the techinque that culture media of constant composition could 

 be obtained and then modified at will. This has been successful 

 beyond expectation, and results which, it is believed, are of con- 

 siderable interest have been obtained, though time has not yet 

 permitted the carrying out of a full set of analytical experiments. 



The main results of the work have been announced briefly in 

 two preliminary communications read before the Societe de Biol- 

 ogie (Burrows, '10), and since then the author, in collaboration 

 with Dr. Carrel ('10), has described the results of some experiments 

 with adult tissues which were made after the present investi- 



