791 



length of' the ventricukis of one could be calculated to be 2.5 mm. 

 of another 2.25 mm. while of the third dog the longitudinal section 

 measured 3 mm. In the two first cases the greatest depth and breadth 

 were 0.4 — 0.17 mm. and 0.5 — 0.15 mm. respectively, and the great- 

 est depth in longitudinal section 0.515 mm. In longitudinal section 

 jt further appears that the canal does not run quite to the point of the 

 conus, but stops 0.225 mm, from it and that the portion of the canal 

 behind the ventricle exhibits slight differences in depth. Past the 

 conus very small ganglions are seen outside the membranes. 



Felis catix domestica. In general we find here the same conditions 

 as in the dog. Owing as the fissura anterior disappears earlier the 

 section does not show the kidney shape after the heart shape, but 

 the conus here is more or less flattened at both poles, and later it 

 becomes oval and pear-shaped on section. Further the central caiuil 

 in the cat appears to have different diameter measurements at several 

 places, and is mostly obliterated. At first fusiform on section with 

 a depth of 0.30 ram. and a width of 0.1(36 mm. towards the back 

 it becomes roundish, with a section of 0.230 mm. and then points 

 in a ventral direction. At several places it exhibits small folds 

 in many sections of the venlriculus, these are symmetrically present 

 in the posterior third portion (fig. 18). Here the ventricle is 0.558 mm. 

 deep and 0.250 mm. wide, after which it gradually narrows to a 

 fine cleft which has also small folds. The whole venlriculus is 

 2.25 mm. long. At the end of the conus a few ganglion cells are 

 observed. 



We see thus that of our domestic animals the horse exhibits 

 various peculiarities in the structure of the conus. Although the length 

 of the ventriculus terminalis is very small com[)ared to that of 

 human beings at least, (man 8 — 10 mm., horse 5.5 mm.) this differ- 

 ence is certainly fully compensated by the particularly strong folds 

 of the ventricle walls and the numerous, frequently even strongly 

 developed folds of the canal before the ventricular widening. 

 This fold formation can be seen in a more or less degree in all 

 the other domestic animals with the exception perhaps of the pig, 

 but in none in such a degree of development as in the horse. 

 Further the rupture of the canal, the presence in the horse of a 

 neuroporus posterior and the striking abundance of blood-vessels in 

 the immediate proximity of the central canal. As regards the rupture, 

 Stilling has observed that the central canal breaks through at the 



51 



Proceedings Royal Acad. Amsterdam. Vol. XVIll. 



