DUCTLESS GLANDS IN THE CHICK. 
299 
The Development of the Trabecular Tissue. 
The development of the trabeculse commences as early as the eighth day of incu- 
bation ; previous to this period the chief mass of the substance of the spleen is made 
up of nuclei, containing in their interior one or more dark dotted granules ; at this 
period, however, spindle-shaped pale granular fibres, containing in their centre an 
oval elongate nucleus, with a nucleolus, may be observed sparingly tliroughout the 
substance of the organ. On the ninth day, similar but more numerous fibres may 
be observed, either separately or in delicate cylindrical, or riband-like bundles. By 
the fourteenth day these fibres have increased very considerably in quantity, forming 
innumerable fine fibrillated bands, intersecting the entire substance of the organ, 
much as in the adult state. 
On the Development of the Blood-Vessels and the Blood. 
The blood-vessels which supply the spleen, the separate vessels of this organ, and 
the blood, have a completely separate, though concurrent development. They are 
all observed about the eighth day of incubation (fig. 7)- The splenic artery, which 
is developed a little previous to the vein, may be now observed as a delicate white 
tract of blastema, running from the inferior and posterior angle of the spleen to the 
descending aorta ; on arriving at the inner side of the organ, a prolongation of the 
same colour may be observed passing to the upper end of the stomach, just beneath 
the proventriculus, and one or two to the front of the same organ ; it then runs along 
the inner margin of the spleen, and is ultimately lost in the substance of the pan- 
creas and in the duodenal fold. No similar tract could however be found, after- 
repeated examination, to pass into the substance of the spleen, although at the same 
period capillaries containing pei-fectly formed discs, but as yet having no proper- 
coats, and apparently mei’ely formed by the walls of cells agglomerated together, 
were seen to be arranged in a branching manner throughout the substance of the 
organ. On the ninth day this vessel presents a reddish tinge, and its disti-ibution is 
the same as in the adult bird. Two small branches are now observed to be given 
oflF to the substance of the spleen, from the vessel previously described, as it runs 
along the inner side of tire organ. The splenic vein makes its first appeai-ance on 
the thirteenth day, in the form of a reddish white tract of blastema, which runs 
forward and joins with the left side of the mesenteric vein, which is formed on the 
twelfth day. On the fourteenth day, the splenic vein consists of three small branches, 
larger than the arteries, which, uniting together, empty themselves into the mesen- 
teric vein. 
The development of the blood-globules in the spleen, as well as the various 
changes they undergo in the substance of this organ, are points of the very highest 
import, from the great difference of opinion that at present exists regarding its use, — * 
Gerlach and Schaffner believing that the spleen is the organ in which the blood- 
