THYMUS AND THYROID BODIES. 
641 
i. The allantois, 
j. The omphalo-mesenteric artery, and 
h. Omphalo-mesenteric vein ; traces of the umbilical vessels are also 
seen in the parietes of the abdomen. 
l. The liver and intestinal tube. 
m. Lungs. 
Fig. 4. Jugular veins and lateral masses of blastema in the Sheep, soon after the 
latter have joined across the middle line. 
a. The triangular absorption of the cervical portion, which is the first 
indication of the separation of the thyroid. 
Fig. 5. The next stage, in which the thyroid is more distinct. 
Fig. 6. The thyroid is now quite distinct and differs from the thymus in being opake ; 
the latter exhibits opake spots in a semitransparent matrix. 
Fig\ /• The thyroid and thymus have assumed their perfect form. 
Fig. 8. A portion of the supra-renal capsule of the adult green Monkey, slightly com- 
pressed. It exhibits the minute nucleated particles of which it consists. 
Among these, at pretty regular distances, are seen the germinal spots. 
Fig. 9. A portion of the thymus of the Brown Bear, slightly compressed. It exhibits 
the nucleated particles of which it consists. These are grouped in spherical 
masses around centres from which they appear to have derived their origin. 
Fig. 10. A portion of the thymus from a human foetus. It has been taken from the 
surface of the gland, so as to exhibit the areolar fibres which form its deli- 
cate capsule. The pressure of the glass plates has almost obliterated the 
spherical grouping of the cells. 
Fig. 11. A portion of the membrane which covered the contiguous surfaces of the 
lobes of the thymus of a human foetus (the membrane lining the reservoirs 
of Sir A. Cooper). It has the same structure as in fig. 10. It exhibits no 
germinal membrane, blit consists of an areolar or fibrous texture intermixed 
with the cells of the organ, the fibres being more fasciculated, and running 
a straighter course than in the substance of the organ. 
Fig. 12. A portion of the thyroid from a human foetus, slightly compressed. It ex- 
hibits the same structure as the thymus, but its fibrous texture is more 
developed. 
Fig. 13. A portion of the same thyroid to show its vascular net-work, in the meshes 
of which, as in fig. 12, the cells are seen arranged in groups. 
4 o 
MDCCCXLVI. 
