134 TEIJI HOSHINO 



No round-cell infiltration is seen surrounding the central 

 canal. Sometimes there seems to be a slight increase of 

 neuroglia at the periphery along the medial sulcus in the funic- 

 ulus posterior in a few sections; however, this is not seen in 

 successive series of preparations. Lissauer's zone and both 

 spinal roots in all the affected birds show no evident difference 

 from the normal. 



2. Cerebellum 



The cerebellum of the pigeon lies as a dorsal cover of the 

 fourth ventricle and anteriorly it is attached closely to the 

 large optic lobes. It has a spherical shape and is supported 

 on both sides by a stalk, the crus cerebelli ad medullam (Stieda, 

 '69). This is the only cerebellar peduncle the pigeon has, any 

 independent structure corresponding to the other two peduncles 

 in mammals is not defined, at least macroscopically. The 

 lamellae of the cerebellum, which run transversely on the sur- 

 face, converge in the crus cerebelli, fan-shaped at the lateral 

 part of the cerebellum. The lateral hemisphere is not present 

 in the pigeon. As to the division of the vermis, Shimazono 

 ('12) divided it into two parts, the vermis anterior and posterior; 

 Ingvar ('18) lately divided it into the lobus anterior, medius, 

 and posterior. The anterior, Ingvar divides from the medius 

 by fissure primarius and the posterior from the medius by the 

 fissure prepyramidalis. He came to this division as a result 

 of his phylogenetic and ontogenic studies. The lobus anterior 

 is divided into four lobuli; lingula, lobus centralis, and culmen, 

 and the lobus posterior into three lobuli; uvula, nodulus, and 

 pyramis. The interplaced lobuli between the anterior and 

 posterior comprise the lobus medius which consists of three 

 lobuli. 



A small appendix from the posterolateral portion of the cere- 

 bellum turns up, making a furrow between it and the cerebellar 

 body; it is shaped like an auricle, and is called the lobus lateralis 

 or auricle. Many authors agree that it corresponds to the 

 floccular body in mammals. The auricle consists of two main 

 lamellae, the one large anterior, the paraflocculus, the other 



