BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 135 



small posterior, the flocculus. The former is continued from 

 the uvula and one part of pyramis, while the latter comes from 

 the nodulus. 



A majority of the specimens were cut transversely and there- 

 fore at first there appears in the sections the lobuli of the lobus 

 posterior, then the middle part of the vermis and the medullated 

 cerebellar body, and at last the lobus anterior comes into view. 

 Here it must be noticed that in the affected cerebellum, owing to 

 its small size, when we start to cut sections from the same sur- 

 face at the same time with a normal cerebellum, both being at 

 the same level in a piece of paraffin mounting, we reach the white 

 substance of the affected cerebellum with the knife before we 

 reach to the same white substance of the normal. 



Each lobule of the cerebellum of all the affected birds was 

 measured and compared with that of the normal birds. The 

 chief result is the greater or less reduction of the cortex cere- 

 belli, especially of the molecular layer in almost all parts of the 

 cerebellar surface. This is found to be true in all the affected 

 pigeons. The reduction of this molecular layer is general; 

 the vermis anterior, medius, posterior as well as auricle are 

 generally affected. We can hardly deduce any rule concerning 

 the situation of the reduction of this layer except that in all 

 cases it is somewhat marked and constant in the lateral gray 

 matter of the central medullary substance (Kleinhirnkorper) 

 which will be described later. In none of the affected birds 

 is there ever found any place where the molecular layer is totally 

 absent. 



The granular layer and the medullated layer are usually 

 slightly narrower than normal, but the difference is not so 

 striking as in the molecular layer. The granule cells present 

 normal character. The Purkinje cells show generally no change 

 either in size or in number. No cell is seen that has undergone 

 any process of disintegration. The arrangement of the Nissl 

 substance in the cell is almost normal, though it appears in 

 much less quantity when compared with that of the normal. 



The nucleus cerebellaris lateralis appears in the section of 

 the cerebellar body at the level where the intrabulbar vestibular 



