Stroud, Mmnmalian Cerebellum. 1 1 1 



Figs. 40 and 41. Sagittal sections through the cerebellum of an embryo 

 kitten 93 mm. long. Compare with Pigs. 17 and 20, PI. II. Shows a section 

 through the U-bend including, 



a. Supraflocculus ) r- .■ . .. c ..\, a i 



, A< i-xi 1 y Constituents of the paraflocculus. 



b. Meditlocculus / ^ 



c. Flocculus. 



d. Kilos, plexus, tela, parepiccele and cestus. 



e. Auditory region. 



Fig. 41. A section a little farther mesad includes the tip of the pre- 

 pileum. 



PLATE IV. 



Fig. 42. Mesal aspect of the cerebellum of an embryo kitten 45 mm. long. 

 Shows the condition of the parts at this early stage. The ental surface of the 

 cerebellum is now concave instead of convex. Compare Figs. 31, 35, 36, 37, 

 PI. Ill ; also Figs. 43, 44, PI. IV. It certainly looks as though the cerebellum 

 had rotated caudo-ventrad. This seems to me the simplest and most logical ex- 

 planation of the change in the position of the ripa from that shown in Figs. 31, 

 34, 35, PI. Ill, to the position shown in this figure. Note the relative thick- 

 ness of the valvula and metatela, also the position of the plexus, and the 

 floccular and uvular sulci. 



Fig. 4:^. Mesal aspect of the cerebellum of an embryo kitten 55 mm. long. 

 Shows essentially the same features as Fig. 42, and in addition the furcal sulcus 

 which divides the cerebellum into two great divisions, the preramus and post- 

 ramus. The former presents three sulci while the latter shows only one, the 

 uvular sulcus. Contrast with Fig. 42, where the only one present is a very 

 slight depression, the uvular sulcus. Note also the small volume of the cere- 

 bellum as compared with that of the oblongata in all stages up to this period. 



Fig. 44. Mesal aspect of the cerebellum of an adult cat, No. 753 (x about 

 4). Shows the general structure of the mesal part of the cat's cerebellum 

 which is quite like the condition found in man. The most striking feature, on 

 first sight, in the arbor, whose treelike branching is so characteristic of sagittal 

 sections through the organ. It consists of a short thick trunk supported upon 

 two lateral roots, or peduncles, and of two enormous branches, between which 

 is the furcal sulcus. This sulcus forms a natural division and separates the 

 cerebellum into two great regions. The cephalic is the preramus, the caudal is 

 the postramus ; the latter forms the greater portion of the cerebellum. 



As for the mesal part, or vermis, so much of it as is a part of the preramus 

 is the prevermis, the remainder is the postvermis. In previous works all of the 

 vermis cephalad of the peduncular sulcus has been called prevermis, but if we 

 are to be governed by natural divisions, the prevermis ends at the furcal sulcus. 



Each ramus is divided into smaller branches or lobes practically the same 

 as in man where they have been given specific names. The same terms are 

 applied to the regions which the writer considers homologous in the cat. It is 

 interesting to note that apparently the pyramis is rudimentary in the cat, and 

 that there is an additional lobe in the cephalic part of the prevermis. The 

 writer suggests for it the term cephalic lobe. This subject will be further dis- 



