781 



medullaris readies the second lumbal segment, in the carnivori this 

 passes the whole or almost all of the lumbar region of the vertebral 

 column, which in these animals is generally built up of seven, 

 sometimes of 6 vertebrae, while in the Ungulata, it can be traced as 

 far as the middle of the sacral portion of the vertebral column. 



Similarly, the continuation of the conus and that of the surrounding 

 membranes, the (ilum terminale, extends in these animals, owing 

 to the stronger development of the tail column, further than in the 

 corresponding part of the human body. 



Ei/uus cahnllns. In the last lumbal segment the transverse section 

 of the medulla of the horse shows a heart shape, with the basis 

 turned ventrally (anterior) and the blunt point dorsally (posterior). 

 The anterior horns are well developed, the posterior horns are 

 large, with rounded, 'much broadeneii lops turned towards the 

 periphery ; the substantia gelatinosa is characterised by a sharply 

 ontlined fibre system. As well as in the ventral and in the 

 ventro-lateral portion of the anterior horn, numbers of large 

 cells are met with on the border of the anterior and posterior 

 horns; in the posterior horn we see scattered cells generally of a 

 somewhat smaller type. Occasionally these are fusiform or egg-shaped, 

 or more or less round, and they exhibit a marked accumulation of 

 pigment, which causes a morphological resemblance to the cells of 

 the spinal ganglion of the horse. Frequently we see a few cells, 

 sometimes clustered in small groups and of a narrow fusiform, in 

 the border zone of the posterior horn, most of them on its posterior 

 and outside edge. The septum longitudinale posterins is very thin 

 and the iissura longitudinalis anterior much narrower on the periphery 

 than in the more central portion of it (fig. 1). The canalis centralis 

 is not obliterated, small coagulations are visible in the centrum but 

 the ciliated epithelium is quite intact. Remarkable is the great 

 number of small blood-vessels situated in its immediate neighboiu-- 

 hood. It shows a peculiar form (fig. 2). The posterior portion of it is 

 broad and rounded, and possesses two small |)ointed lateral recessus, 

 the anterior portion is smaller and likewise rounded off. At its 

 greatest breadth it measures 0.315 mm., while the greatest depth 

 is 0.365 mm. At the commencement of the sacral medulla the 

 heart shape becomes more distinct on section as the posterior pole 

 becomes more pointed. The canalis has shifted from the centrum in 

 a forward direction and has become rather narrower ; the above 

 dimensions now are 0.216 mm. and 0.315 mm. respectively; the 

 section is that of a spindle with irregular walls, and the side pro- 



