130 TEIJI HOSHINO 



of fibers around the cells is not pronounced, though a few tiny- 

 bundles enter from the dorsal roots and from the funiculus pos- 

 terior. Schacherl ('02) says the small size of this column in the 

 pigeon makes it difficult to study the internal structure of the 

 individual cells, and he says that the cell group in the upper 

 cervical cord which corresponds to Clarke's column cannot be 

 distinguished, 



In the upper enlargement, cervical intumescentia, is found an 

 analogous structure to Clarke's column in full development, but 

 this is different from the arrangement in man and other mammals, 

 for in these it does not appear at this level. It has a large spheri- 

 cal form on each side at the base of the dorsal horn, having its 

 larger diameter from the medio ventral to the latero dorsal side 

 and its shorter diameter from the mediodorsal to lateroventral 

 side. Its huge structure, 0.334 to 0.384 mm. in diameter in 

 the average normal pigeon, occupies almost the whole space of 

 the gray matter at the base of the dorsal horn. The marked pro- 

 trusion into the white matter of the posterior funiculus as seen 

 in man does not occur in the pigeon; the whole group of cells is 

 within the horn or in the central gray matter and causes no 

 bulging. 



The cells are generally round, oval, sometimes polygonal; they 

 vary in number from ten to eighteen, and among them there are 

 three to six large cells in each average section. The size of these 

 large cells in the normal varies from 31.3 to 51.3 /x in diameter. 

 The area of this cell group is filled and surrounded by a mass of 

 fine network of fibers which is mainly composed of fibers from 

 the posterior roots and fiber bundles from the funiculus dorsalis. 

 This network of fibers gives the dorsal and medial borders of the 

 column a clear definition from the surroundng tissues. The 

 ventral and lateral borders, however, are not quite so well 

 defined, owing to the diffuse transition into the lateral proprial 

 fasciculus or into the fiber network of the lateral portion of 

 the central gray matter. 



In the thoracic region the column decreases in size, the con- 

 tained cells are less numerous and the network not so luxuriant, 

 but in the lower enlargement, intumescentia lumbosacralis, it 



