Volume XII 1902. Number 4 



THE 



Journal of Comparative Neurology. 



ON THE ORIGIN OF NEUROGLIA TISSUE FROM 

 THE MESOBLAST. 



By Shinkishi Hatai. 



{From the Neurological Laboratory 0/ the University 0/ Chicago.) 

 With Plate XVII. 



It is now generally believed that the neuroglia cells in the 

 central nervous system are produced by cell division from either 

 germinal cells in the ectoderm which lines the primitive neural 

 canal or from their direct descendants. In other words, all the 

 neuroglia cells, as well as the nerve cells, have the same origin, 

 both arising from the ectoderm. 



Opposed to this idea is the report of Capobianco and 

 Fragnito ('98) of a second source of the neuroglia, namely the 

 mesoblast. According to them, in an early embryonic stage, a 

 large number of the mesoblastic cells forming the meninges 

 migrate into the central nervous system or are carried in by the 

 blood capillaries, and finally become transformed into the neu- 

 roglia cells. This conclusion was reaffirmed very recently by 

 Capobianco (oi) and his observations further extended. 



While the present writer was examining the preparations 

 of embryonic brains of various animals, his attention was drawn 

 to the fact that the neuroglia cells are produced not only in the 

 manner reported by Capobianco and Fragnito, but that a large 

 number of these cells, in a later embryonic stage, are formed 

 by the proliferating cells of the capillary walls. The conclu- 

 sion that some of the neuroglia cells are derived from the cap- 

 illary walls is based on the following observations. 



The materials used for the investigation were white rats 

 having body-weights of 3.5 and 4.5 grams respectively, and 



