Ossification Process in Birds, &g. By Dr. L. Schbneij. 69 
Studying the vertical sections of young animals, under slight 
magnification, the following will be seen : 
Fig. 1. On the free part of the cartilage which forms the front 
of the knee-joint, also near the perichondrium, are seen spindle- 
shaped and elongated cartilage corpuscles (aj, by degrees changing 
into round cartilage cells, having distinct nuclei. The latter form a 
large stratum (h) which appears to be intersected by vascular 
cartilage, which forms marrow-spaces (c) of the most various forms. 
Joined to the stratum of round nucleated cartilage corpuscles is a 
narrow layer, formed of small flat cartilage bodies {d), which is 
invariably coloured yellowish red, and immediately joins the true 
bony border. The bone formation of the elementary substance (e) 
produces a handsome structure, going over into the first-formed 
small beams of the bone tissue (/). The latter border the marrow- 
spaces {g) of the bony epiphyses (Epiphysenknockens). 
Under greater enlargement (Fig. 2) one observes that the lime 
structure {e) reaches, in its uppermost little pointed processes, to 
the layer {d). In the interior of the lime structure the cartilage 
corpuscles are distinctly visible. In difierent spots the small bone 
beams reach directly up to the lime structure, without any sharp 
defined border being recognizable between both ; the bone, however, 
being sufficiently distinguished by the layer of bone-corpuscles in 
it. The marrow-spaces {g) are filled with round, oblong, or spindle- 
shaped marrow elements, besides which there are often found 
various large, evenly granulated protoplasma layers, either with 
many nucleated or non-nucleated so-called Myeloplaxes (Kobin). 
Spindle-shaped elements are most frequently found in the centre of 
a marrow-space, where they are connected with blood-vessels, as I 
shall show hereafter. 
The marrow formation can best be followed in horizontal 
sections (Fig. 3). First we observe that in certain spaces a secretion 
of the cartilage elementary substance (e) takes place. The im- 
mediate transformation of the cartilage into free protoplasm with 
formation of lustrous small lumps (h h) which fill the marrow- 
spaces, cannot, it is true, be directly observed; however, we are 
bound to conclude that it does take place, because the marrow-spaces 
are surrounded on all sides by cartilage tissue, and the lime 
structure broken up, as it were, reaches into the marrow-spaces. 
It can be observed that first of all a cartilage-tissue unit (terri- 
torium) appears deprived of all its lime salts, and next to it, 
apparently through direct transformation of the cartilage cor- 
puscles, emerge marrow elements, whilst immigration from the 
periosteum at such a distance cannot be thought of. Just as 
little is an immigration from the blood-vessels to be supposed, such 
as, amongst others, A. L. Eollet took for granted, because in the 
newly-formed marrow-spaces there are no blood-vessels to begin 
