300 
MR. H. GRAY ON THE DEVELOPMENT OF THE 
discs are formed during' extra-uterine life, whilst Kolliker, Beclard and Ecker, 
suppose that the blood-globules are destroyed there. The blood-discs in the spleen, 
as I have already mentioned, make their first appearance in this organ about the 
eighth day. They are oval or circular, varying somewhat in size, and consisting of 
an external envelope, pale, homogeneous and indistinct, having a nucleus on its wall, 
which is dark, highly refractive, irregularly circular, and in some cases of a granular 
texture. Some of these globules may be distinetly seen in an incipient stage of 
formation, and eonsist of a dark, and at first, a somewhat irregular granular nucleus, 
around which a delicate cell-wall may be observed. Although I have observed this 
in several cases, I do not presume the spleen to be the organ in which the develop- 
ment of the blood-globules takes place during intra-uterine life, nor have I observed 
that the development of the blood-discs continues to take place in it after its con- 
nection with the general vascular system is effected. With regard to the disintegra- 
tion of the blood-globules, after the most repeated and careful examinations, I have 
failed in detecting anything that would lead me to suppose that this organ can, 
during its progress of development, perform the function Kolliker and others have 
assigned to it in its adult state. 
On the Developinent of the Pulp. 
The entire substance of the spleen at an early period of its development is almost 
preeisely similar in structure with the supra-renal and thyroid glands, with which it 
may consequently be allied. As the evolution of the organ proceeds, part becomes 
developed into trabeculae, part into blood-vessels and blood, whilst the greater por- 
tion remains to form the essential element of the organ, the pulp tissue. On the 
fifth day this substance presents the following elementary composition. It is com- 
posed of nuclei, varying in form and size. The greater majority are irregularly 
circular, their sides and edges being flattened at some points, so as to give them an 
angular form ; some, however, are perfectly circular ; they are pale, and their outer 
margins dark and well-defined, whilst in their interior may be observed, one, two, 
or more dark granules. These form a very considerable portion of the substance of 
the pulp, not only at this, but also at every other period of its development. A few 
nucleated spherical vesicles may also be observed, their outer margin exceedingly 
delicate ; and on their wall may be seen a small irregular dark-edged nucleus ; some- 
times the nucleus is more circular, and contains a nucleolus, whilst the interior of 
the vesicle contains a few delicate pale granules. With the exeeption of a few small 
dark and highly refraetive oil-granules, and a fine pale granular plasma, in which 
the above elements lie, they constitute the entire mass of the pulp tissue at this 
period. The next change observable takes place concurrent with the formation of 
the vessels which supply the organ, and whieh is soon followed by an increase of its 
size. Now, besides the elemen-ts already described as forming its structure, there 
maybe observed nuclei, similar to those constituting the pulp at an early period, but 
