VASCULARITY IN THE NERVOUS SYSTEM 459 



SUMMARY 



No exact quantitative comparison of the vascularity of different 

 parts of the central nervous system has been published hitherto, 

 and the present study is an attempt partly to fill this gap. To 

 that end, anatomical measurements of the capillary richness 

 have been made in twenty-one regions arbitrarily selected in 

 the spinal cord, medulla oblongata, and cerebellum of the albino 

 rat, and the values obtained and their ratios are presented in 

 tabular and graphic form. It is not claimed that these values 

 represent the absolute vascularity of the parts concerned, but 

 it is believed that they do show in a fairly reliable manner the 

 relative richness of the capillary supply. The results may be 

 summarized as follows: 



1. The gray matter is much more richly supplied with capil- 

 laries than is the white matter, the poorest part of the gray 

 being nearly half as rich again as the richest part of the white 

 among the regions studied. 



2. All parts of the white matter are not equally vascular, the 

 pyramidal tract, the richest part in the spinal cord, being about 

 twice as rich as the fasciculus cuneatus, while the fasciculus 

 longitudinalis dorsalis in the medulla is still richer. 



3. The gray centers can be sharply divided into two groups, 

 the motor nuclei and the sensory and correlation centers, of 

 which the latter are richer than the former. Though the richest 

 motor region (ventral cornu) is but little poorer than the poorest 

 sensory one (spinal V nucleus), the two groups do not overlap 

 in the case of those regions studied, except in a few individuals. 

 The substantia gelatinosa Rolandi of the spinal cord is the only 

 part which does not conform with this statement. 



4. The richest of the centers observed is the dorsal cochlear 

 nucleus, which is more than half as rich again as the ventral 

 cornu, about two and a half times as rich as the substantia 

 gelatinosa Rolandi (the poorest gray region), and eight times as 

 rich as the fasciculus cuneatus. 



5. Great individual variations occur, and the two sexes do 

 not seem to show any constant difference. 



