THYMUS GLAND. 723 



contains numerous dotted corpuscles, similar to those found in the chyle. The 

 corpuscles are flattened circular disks, measuring about T7 Vtf of an inch in dia- 

 meter. 



Vessels and Nerves. The arteries supplying the thymus are derived from the 

 internal mammary, and from the superior and inferior thyroid. The veins termi- 

 nate in the left vena innominata, and in the thyroid veins. The lymphatics are 

 of large size, arise in the substance of the gland, and are said to terminate in the 

 internal jugular vein. Sir A. Cooper considered that these vessels carried into 

 the blood the secretion formed in the substance of the thymus. The nerves are 

 exceedingly minute ; they are derived from the pneumogastric and sympathetic. 

 Branches from the descendens noni and phrenic reach the investing capsule, but 

 do not penetrate into the substance of the gland. 



Chemical Composition. The solid animal constituents of the thymus are albu- 

 men and fibrin in large quantities, gelatin and other animal matters. The salts 

 are alkaline and earthy phosphates, with chloride of potassium. It contains about 

 80 per cent, of water. 



